Apparatus and method for determining an eye property

ABSTRACT

An apparatus, and corresponding method, for determining a property of an eye includes a housing with a proximal port that receives an eye and also light from the eye. The housing further includes a distal port, and the two ports together form a visual channel providing an open view to enable the eye to see target indicia external to and spaced away from the housing. A wavefront sensor within the housing is configured to receive the light from the eye via the optical path and to measure a wavefront of the light. A determination module determines an objective refractive correction based on the wavefront and predicts a subjective refractive preference of a person having the eye based on the objective refractive correction. Embodiments can be handheld, and binocular, and predict subjective refraction based on demographic and other information.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/309,169, filed Dec. 12, 2018, which is the U.S. National Stage ofInternational Application No. PCT/US2017/037257, filed Jun. 13, 2017,which designates the U.S., published in English, and claims the benefitof U.S. Provisional Application No. 62/350,018, filed on Jun. 14, 2016.The entire teachings of the above Applications are incorporated hereinby reference.

GOVERNMENT SUPPORT

This invention was made with government support under SBIR1R43EY025452-01A1 and SBIR 2R44EY025452-02A1 from the National EyeInstitute of the National Institutes of Health. The government hascertain rights in the invention

BACKGROUND

Optometrists or ophthalmologists performing eye examinations in a clinictypically use a phoropter (or equivalently, a trial lens set) todetermine which of many fixed lens settings produces the best eyesight,subjectively, for a given patient. However, this is a lengthy processdue to the iterative nature of the subjective refraction. To speed upthe process, objective measurements using a separate instrument areoften used to reduce the number of iterations needed for subjectiverefraction with the phoropter. The relatively quick objectivemeasurement of the refractive status of the eye serves as a goodstarting point for subjective refraction. Autorefractors are a commontool to perform such objective measurements of the eye. Wavefrontaberrometers are a type of autorefractor which have been used in clinicsto make objective determinations of eye aberrations. However, becausewavefront aberrometers are typically more complex and expensive thanother types of autorefractors, they have not typically been used forproviding an initial starting for subjective refraction. Besides typicalaberrations used for prescribing eyeglasses (defocus and astigmatism),wavefront aberrometry can also determine aberrations of higher orderthan phoroptry.

More recently, portable devices for performing wavefront aberrometryhave been developed. These devices have the potential advantage ofmaking refractive eye care more available and affordable, particularlyin locations with few eye care providers.

SUMMARY

Existing portable wavefront aberrometers have several disadvantages.First, they do not allow a patient to view through the device so thatthe patient's eyes can automatically tend toward a relaxed,unaccommodated state. To counter this, cycloplegic drops can be used todisable accommodation. However, this treatment includes side effects andrequires waiting time between treatment and aberrometry measurements.Another approach to relaxing accommodation is to “fog” the eye. However,this approach also has limitations and is not effective for all eyepatients.

Furthermore, existing portable wavefront aberrometers (i) do not providephoroptry measurements, which take into account a patient's subjectivepreference, which is typically slightly different from the correctionindicated by purely objective measurements, or (ii) are not open view,allowing a patient to see through the device to a target external andspaced away from the device. Phoropters are typically large, bulky,heavy, and involve motion and vibration when lenses are switched, andall of these characteristics are undesirable in environments wherehandheld devices are used. While subjective refraction is considered the“gold” standard in evaluating patients for refractive correction, thephoropter is usually not used in environments where handheld portablewavefront aberrometers are employed. Instead, trial frames and lensesare used, which can be slower and more cumbersome to use.

While tunable lenses have been proposed for use with certain worn orportable devices, it is known that tunable lenses in many instances lackthe precision of fixed lenses. Yet even with a multiple-fixed-lensphoropter-type system, wavefront aberrometry is still highly desirablefor determining both lower- and higher-order corrections objectively,and the phoroptry and wavefront aberrometry functions haveconventionally been performed using separate devices.

Embodiments described herein can overcome the limitations of existing,separate phoroptry and wavefront aberrometry systems by performing thesame functions in the same unit. Furthermore, in many respects, bettereye analysis and examination is possible using embodiment apparatusesand methods than is possible with two separate instruments for phoroptryand wavefront aberrometry, whether in a clinical setting or a field-usesetting. Example advantages of embodiments include increased examinationspeed, more accurate refractive results, increased flexibility inpatient and clinician use, and the ability to obtain wavefrontaberrometry measurements at arbitrary times during phoroptry andaccommodation measurements. Moreover, embodiments including portableapparatuses can even be configured to perform lensometry measurements.Embodiment apparatuses and methods can also provide patients with anindication of how their vision will improve with lenses havingrefractive corrections that are determined by the same system based onobjective wavefront aberrometry, subjective phoroptry measurements, orboth.

Furthermore, embodiments described herein can overcome the limitationsof existing portable wavefront aberrometers by providing open-view,binocular configurations that do not necessarily require the use ofcycloplegic drops or fogging. Embodiment devices and methods can includeusing one or more tunable lenses incorporated into a device to improvethe accuracy of wavefront aberrometry measurements, perform subjectivephoroptic measurements, simulate final refractive correction for thepatient, and perform lensometry measurements. Thus, by combining awavefront sensor and a tunable lens, embodiments described herein canachieve many advantages that have not been achievable with existingdevices that seek to use either one or the other, and these advantageswill become more apparent throughout the description hereinafter.

In one embodiment, an apparatus for determining a property of an eye,and corresponding method, includes a housing having a port configured toreceive an eye (i.e., to serve as a viewing port through which an eyebeing assessed can view) and to receive light from the eye. Light can bereceived from the eye by directing a source of eye illumination lightfrom the apparatus into the eye and then collecting light that isthereby reflected or backscattered from the eye, for example. Theproperty of the eye can be a refractive property such as a lower- orhigher-order refractive aberration, a refractive prescription, anaccommodation range, or another refractive property related to eyesight.

The apparatus further includes a visual tunable lens mounted to, orconfigured to be mounted to, the housing to apply a variable focal powerto the light from the eye and to pass the light along an optical path.The apparatus also includes a wavefront sensor within the housing, thewavefront sensor being configured to receive the light from the eye viathe optical path and to measure a wavefront of the light from the eye.The apparatus still further includes a determination module configuredto determine a property of the eye based on the wavefront. The propertyof the eye can be a refractive prescription needed to correct the visionof the eye, a spherical aberration, a cylindrical aberration, an axisfor cylindrical aberration, a refractive error of higher order thanspherical or cylindrical aberrations (i.e., defocus and astigmatism), arange of accommodation, an objective refractive measurement, asubjective refractive preference of a person having the eye, or otherproperty of the eye.

The housing can be configured to be gripped by at least one hand of theperson having the eye (i.e., the person whose eye is to be assessedusing the apparatus) to support a full weight of the apparatus duringuse. The port can be further configured to receive a corrective lensapplied to the eye, and the wavefront sensor can be further configuredto measure the wavefront of the light from the eye in combination withthe corrective lens. The port can be a first port, the eye can be afirst eye, and the housing can further include a second port configuredto receive a second eye of the same person (whose eye is to be assessedusing the apparatus), wherein the housing defines a binocularconfiguration.

The visual tunable lens can be a first visual tunable lens, and theapparatus can further include a second visual tunable lens configured tobe mounted to the housing and to apply a variable focal power to lightfrom the second eye.

The port can be a proximal port, and the housing can further includes adistal port, the proximal and distal ports together forming a visualchannel from the proximal port through the distal port, the visualchannel providing an open view to enable the eye to see target indiciaexternal to and spaced away from the housing through the visual channel.

The apparatus may also include a target light source mounted to thehousing and configured to produce the target indicia external to andspaced away from the housing, the target indicia being viewable by theeye through the visual channel. The target light source can be furtherconfigured to produce the target indicia at a distance of effectiveinfinity from the eye.

The apparatus can further include an eye illumination light source inthe housing, and the eye illumination light source can be configured todirect light through the proximal port and into the eye to produce thelight from the eye via reflection or backscattering from the eye. Alight source tunable lens can also be included in the apparatus and canbe configured to apply a variable focal power to light from the eyeillumination light source. The light source tunable lens can be furtherconfigured to randomize a speckle pattern produced by the eyeillumination light source at the eye or a speckle pattern produced bythe light from the eye at the wavefront sensor. The port may be furtherconfigured to receive the light from the eye non-collinearly withrespect to the light from the illumination light source directed throughthe port and into the eye. Light from the eye illumination light sourcecan be restricted by an aperture that can be included in the apparatus,and a diameter of the aperture can be between about 50 μm and about 500μm.

The visual tunable lens can be configured to randomize a speckle patternproduced by the eye illumination light source at the eye or a specklepattern produced by the light from the eye at the wavefront sensor. Thevisual tunable lens can be further configured to be situated at aspectacle plane of the eye with the proximal port having received theeye.

The determination module may be further configured to determine arefractive correction to be applied to the eye, or to determine one ormore wavefront errors of higher order than defocus and astigmatism. Thedetermination module can be further configured to determine a lenswavefront error due to the visual tunable lens for calibration, or todetermine an accommodation range of the eye as a function of a pluralityof wavefront measurements of the light from the eye.

The housing can be configured to receive a lensometer attachment, andthe lensometer attachment may be configured to support a corrective lensintended to be worn by a person, or a lens blank intended to bemanufactured into a corrective lens. The determination module can befurther configured to determine to determine a refractive property ofthe corrective lens or lens blank based on a lens wavefront of lightreceived through the corrective lens or lens blank.

The apparatus can further include a closed-loop control circuitconfigured to adjust the variable focal power of the visual tunable lensiteratively in response to successive wavefront measurements to minimizea wavefront error of the light from the eye. The apparatus can furtherinclude a control circuit configured to adjust the visual tunable lensin accordance with a subjective refractive preference of a person havingthe eye. The apparatus can also include a manual control configured tobe adjustable by a person having the eye, or someone else helping theperson having the eye, to adjust the variable focal power of the visualtunable lens in accordance with a subjective refractive preference of aperson having the eye.

The apparatus can include a reporting interface configured to report aprescription for refractive correction of the eye. The apparatus canalso include a communication interface configured to query a personhaving the eye, or receive a response from the person, regarding asubjective, refractive preference. The apparatus can also include afixed lens configured to be attached to the housing and to apply a fixedfocal power to the light from the eye to shift a range of refractivecorrection measurement of the apparatus, or a fogging lens configured tobe attached to the housing and to fog a view of the eye.

The sensor module or determination module can include a cellular phone,or the apparatus can further include a cellular phone configured to beattached to the housing or to display a representation of the wavefrontof the light from the eye. The wavefront sensor can include a pixelarray of a cellular phone.

The apparatus can also include cross-polarizers disposed within theoptical path.

The visual tunable lens can be further configured to apply a variablespherical power, astigmatic power, and axis mutually independently. Thevisual tunable lens can be further configured to apply a sphericalequivalent power, vertical Jackson cross cylinder, and oblique Jacksoncross cylinder mutually independently. The visual tunable lens caninclude at least one of a liquid-filled lens, an electro-wetting lens,an Alvarez lens pair, spatial light modulator, deformable mirror, lenswith power that varies spatially, a multi-lens system that changes lensdistances to tune optical power, or a tunable Fresnel lens. The visualtunable lens can include a two-element optic configured to apply thevariable focal power as a function of lateral or rotational displacementof the two elements with respect to each other.

The property of the eye can be an objective property based on thewavefront, and the determination module can be further configured topredict a subjective refractive preference of a person having the eyebased on the objective property. The determination module can be furtherconfigured to predict the subjective refractive preference based furtheron a demographic or physical attribute of a person having the eye.Demographic attributes can include at least one of an age, gender,ethnicity, weight, height, occupation, or another demographic attributeof the person having the eye. Physical attributes can include at leastone of a retinal image quality, axial length, iris color, topography,corneal curvature, aberration of higher order than spherical orcylindrical aberration, or another attribute of the eye. Thedetermination module can be further configured to predict the subjectiverefractive preference using a correlation developed from a databaseincluding respective demographic or physical attributes and respectiveobjective eye properties of a plurality of eye patients.

In another embodiment, a method for determining a property of an eye,and corresponding apparatus, includes applying a variable focal power tolight received from an eye, via a port of a housing configured toreceive the eye, using a visual tunable lens. The method also includespassing the light from the eye along an optical path, as well asmeasuring a wavefront of the light from the eye, the light received viaan optical path from the port. The method further includes determining aproperty of the eye based on the wavefront of the light from the eye.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating an embodiment apparatusfor determining a property of an eye.

FIG. 2 is a schematic block diagram illustrating an alternativeembodiment apparatus that is open view and also includes other optionalfeatures.

FIG. 3 is a schematic diagram illustrating various optional input andoutput features of embodiment devices, such as those illustrated inFIGS. 1-2.

FIG. 4 is a computer interconnect diagram illustrating variouscomponents of the determination and control module in FIG. 2 and itsconnections to various components, including some components illustratedin FIG. 2, some optional components shown in FIG. 3, as well as somethat are not illustrated in FIGS. 2-3.

FIG. 5A is a top-view illustration of an embodiment, binocular,wavefront aberrometer autorefractor apparatus with a lensometer moduleattached; the apparatus of FIG. 5A is also referred to as “QuickSee”apparatus herein).

FIGS. 5B-5C are side-view illustrations of the apparatus illustrated inFIG. 5A. FIG. 5B shows eyeglasses outside of the lensometer module,while FIG. 5C shows the eyeglasses inserted into the lensometerattachment.

FIG. 5D is an exploded, side-view illustration of a calibration cradleand artificial eye that can be used to calibrate the apparatusillustrated in FIGS. 5A-5C.

FIG. 5E is a perspective view of the calibration cradle illustrated inFIG. 5D, with the artificial eye assembly attached thereto.

FIGS. 5F-5K are various illustrations of a calibration cradle assemblysimilar to that shown in FIGS. 5D-5E. FIG. 5F is a side-viewillustration of the assembly, FIG. 5G is a perspective-view of theassembly, and FIG. 5H is an end-view illustration of the assembly; FIGS.5I-5K are various illustrations showing the calibration cradle attachedto the apparatus illustrated in FIGS. 5A-5C.

FIG. 6 is a schematic flow diagram illustrating an embodiment iterativeprocess for minimizing wavefront errors due to aberrations of an eyeusing the visual tunable lens illustrated in FIGS. 1-2 and forsimulating the effects of eyeglasses.

FIG. 7 is a flow diagram illustrating an embodiment procedure fordetermining a property of an eye.

FIGS. 8A-8B are an overall flow diagram illustrating various measurementprocedures that can be performed using embodiment devices such as the“QuickSee” apparatus illustrated in FIGS. 5A-5C.

FIG. 9A is a flow diagram illustrating how embodiment devices andmethods can be used to perform lensometry.

FIG. 9B is a flow diagram illustrating how embodiment apparatus andmethods can be used to suppress speckle in wavefront measurements.

FIG. 9C is a flow diagram illustrating how embodiment devices andmethods can be used to perform objective refraction measurements.

FIG. 9D is a flow diagram illustrating how embodiment devices andmethods can be used to perform subjective refractive measurements.

FIG. 9E is a flow diagram illustrating how embodiment devices andmethods can be used to measure accommodation amplitude for evaluation ofpresbyopia.

FIG. 9F is a flow diagram illustrating how machine learning can beimplemented in embodiment devices and methods to predict subjectiverefractive preferences of an eye patient based on objectivemeasurements.

FIGS. 10A-10B are flow diagrams illustrating parts of a single procedurefor determining subjective refractive measurements (phoroptry) forrefractive eye correction using embodiment devices directly interactingwith a patient.

The foregoing will be apparent from the following more particulardescription of example embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingembodiments of the present invention.

DETAILED DESCRIPTION

A description of example embodiments of the invention follows.

Refractive eye examinations by an optometrist or ophthalmologisttypically involve using a phoropter to determine which of many fixedlens settings produces the best eyesight, subjectively, for a givenpatient. Clinical phoropters are usually binocular (enabling both of apatient's eyes to view through separate sets of lenses) and open-view(enabling a patient to view, through the phoropter lenses, a distanttarget pattern). Typically, the patient is asked to focus on a targetpattern situated a distance of about 20 feet from the patient's eye. Theopen-view design also performs the important function of encouraging thepatient's eyes to remain unaccommodated (relaxed and as optimized aspossible for long-distance viewing) during the measurement. Theunaccommodated state is an important clinical prerequisite for accuratemeasurements for refractive correction of distance vision. Thus, usingtypical clinical phoropters, a prescription for refractive correctioncan be obtained that both (i) corrects for important types of opticalaberrations of the eyes and (ii) takes into account a patient'ssubjective feedback about which correction is preferable.

Wavefront aberrometers, in contrast to clinical phoropters, determine arefractive correction for a patient objectively, without input from thepatient, based on sensing a wavefront of near infrared (near-IR)directed into the eye and reflected or scattered from the retina of theeye. Wavefront aberrometry in an eye clinic can provide informationabout aberrations of the eye of higher order than just sphere andcylinder and is considered a valuable tool in determining refractivecorrection.

Handheld devices have been developed more recently to perform wavefrontaberrometry. A goal of these devices is to enable refractive examinationof people in remote areas without access to standard clinics or eye careprofessionals, as well as to decrease cost of examination and limit thenumber of expensive instruments required, as well as to streamline therefractive examination in high-resource settings. Handheld wavefrontaberrometer devices have some limitations, in that they do not take intoaccount subjective feedback from an eye patient. Further, high-qualityclinical phoropters may not be available to supplement handheld devicemeasurements, due to the cost, size, weight, and mobility limitations ofstandard phoropters.

Moreover, an important clinical requisite for an accurate measurement isthat the patient's eye should be relaxed while the measurement is made.Since existing handheld devices do not allow a patient to view throughthem and focus on a distant object to cause eye relaxation, there are anumber of other techniques that have been used to induce relaxationusing existing non-open view devices. For example, cycloplegic drops canbe placed in the eye to paralyze accommodative control. While effective,these drugs may often have side effects that can be undesirable for thepatient and can require 15 minutes or more for their effects to occur.Another approach is to place lenses in front of the patient's eyes tosimulate myopia (i.e. shortsightedness), referred to as “fogging” thepatient, so that the patient's eye(s) are coerced into relaxing theiraccommodation so as to bring a fixation target into focus. While foggingcan be effective for many patients, some others may not respond well tothis technique. Furthermore, these techniques, even when effective,still do not produce exactly the same results as actually allowing apatient to view a distant target through an open view lens, as is donewith standard clinical phoropters.

Including a set of physical lenses, similar to those of a phoropter,with a handheld device has been attempted. However, this increases cost,weight, and system complexity, and this solution also has feasibilitychallenges because switching between lenses requires at least somemechanical motion or disturbance of a portable handheld device. Thus,this approach would be less mechanically robust and prone to breaking ormis-alignment. Alternative optical approaches such as adaptive optics(e.g., deformable mirrors, spatial light modulators) are prohibitivelyexpensive for application in low-cost diagnostics.

Embodiment apparatus examples can include one or more tunable lensesintegrated into a handheld wavefront aberrometer to act effectively asan on-board phoropter. Wavefront aberrometer measurements can be used asfeedback to the tunable lens, in closed-loop fashion, to automaticallyand quickly adjust a tunable lens through which the patient views tooptimize vision objectively. Because the tunable lens can iterativelycorrect measured wavefront errors until the measured wavefront isnominally parallel, objective wavefront evaluations can be made withgreater accuracy. As will be understood by those familiar withHartmann-Shack wavefront sensors, for example, when the wavefront isnominally parallel, a spot pattern produced by the sensor has spotsnominally uniformly spaced. In this state, uniformity of the spotpattern (and, hence, wavefront errors) can be more exactly evaluatedthan if the spot pattern is very distorted.

After objective autorefraction, feedback from a patient can be used tofurther adjust the tunable lens in accordance with subjective patientpreference to improve the proposed correction. An apparatus cancommunicate with a patient through a variety of methods to obtain thesubjective feedback, even automatically or semi-automatically. Thisfeedback can be obtained and implemented in embodiment devices with orwithout the assistance of a technician or other eye professional.Embodiments can be designed to be self-usable by a single user (i.e.,eye patient) without assistance from a clinician (e.g., anophthalmologist, optometrist, clinical assistant, field technician, orany other person working to assist an eye patient to obtain a correctiveprescription).

Self-usable embodiments are made possible in part because the eye can bealigned with the optics of the device via an external or internalfixation target, or visual or audio cues from the device, or both.Self-usable embodiments can be further enabled by automated orsemiautomated operation of embodiment apparatuses and interactiveinstruction to a patient and saving settings made by a patient. FIGS.10A-10B, as described hereinafter, provide one example of such aninteractive procedure consistent with some embodiment apparatuses.However, embodiments disclosed herein may also be modified and usedadvantageously with clinician assistance to obtain results that aresimilarly unachievable by other handheld units and further unachievableby using mutually separate phoroptry and aberrometry instruments.

Thus, integrated autorefraction and phoropter functions allow thephoropter core (the tunable lens) to be automatically updated based onthe autorefraction wavefront data. Furthermore, when the tunable lens isappropriately situated in or on the device incorporating the wavefrontsensor, the tunable lens can serve as an eyeglass simulation to allow apatient to see through a lens at the appropriate location for aneyeglass with the final, proposed correction prescription implemented.Moreover, certain embodiments can be used to take advantage of thetunable lens to measure accommodation and presbyopia, as well as toperform lensometer functions by measuring optical parameters for a setof eyeglasses already owned by the patient or to be offered to thepatient, for example. Furthermore, the lenses to be measured usingembodiment devices may be lens blanks as well. An optician may want tolocate the optical center position and confirm the power of the lensesbefore cutting the lens blanks to fit an eyeglass frame, for example.

Embodiment devices are preferably “open view,” meaning that the patientcan see through the device to a distant target to relax anyaccommodation of the eye. An embodiment apparatus can be designed tomeasure the aberrations of the user's eye in an unaccommodated state(i.e. the eye is relaxed and focused at infinity). A viewing target maybe located at effective optical infinity, about 20 feet from thepatient's eye. Viewing targets can include a standard eye chart, a spotof light produced by a target light source on the device, or anotherobject in the surrounding environment. Such open view designs can reduceor eliminate the need for cycloplegic drops, and fogging may also berendered unnecessary or optional.

By using a relatively low-cost, electronically tunable lens system,expensive approaches such as adaptive optics can be avoided. Embodimentdevices can also be more mechanically robust and easier to handle andtransport than systems having a set of physical lenses included in aphoropter, for example. A standard phoropter-style or trial frame lenssystem requires lens switching, which can result in fluctuations of thepatient's eye and mechanical disturbances to the wavefront sensorapparatus.

It is noteworthy that available tunable lenses may have lower opticalquality than fixed lenses typically used in high-quality optical systemsfor eye care. For this reason, optical engineers and eye careprofessionals would not generally be inclined to consider using atunable lens in a system designed for high-quality eye examination,whether a phoropter or a wavefront aberrometer. However, the inventorshave recognized that, where a device is designed for a tunable lens towork in combination with a wavefront sensor, the quality of wavefrontaberrometry can be maintained and even enhanced due to iterativewavefront measurements in the presence of automatic, closed-loop,wavefront error cancellation by the tunable lens. Embodiments canprovide wavefront measurements that are captured and processedcontinuously, such as at video rates, for example. Furthermore, awavefront sensor apparatus can be calibrated with respect to anywavefront error caused by a tunable lens, thus enabling measurement ofeven high-order wavefront errors of a patient's eye with high accuracy.Furthermore, as noted hereinabove, a tunable lens also enables fastautomated or semi-automated phoropter, lensometer, and accommodationmeasurement functions on the same device that is used for wavefrontaberrometry, even with a portable, handheld device, and even whentesting is self-administered by the patient.

Embodiments can provide a complete refraction system that enablesrefractive measurements to be performed anywhere by a minimally-trainedtechnician or even by the subject patient himself or herself. This hassignificant global health and industrial utility.

FIG. 1 is a schematic block diagram illustrating an embodiment apparatus100 for determining a property of an eye 106. The apparatus 100 includesa housing 102 having a port 105 configured to receive the eye 106 and toreceive light 108 from the eye. The port 105 is “configured to receive”the eye 106 in the sense that the eye 106 can be placed near enough to,or in contact with, one or more portions of the port such that the light108 from the eye can be received through the port 105. Thus, while theeye 106 is not required to be in contact with the port 105, in variousembodiments, the eye 106 is an eye of a person whose forehead and cheekare placed against an eyecup 104 for registration and mechanicalfixation with respect to the port 105. As a further example, anotherembodiment device having an eyecup configured to come into contact witha person's forehead and cheek is described hereinafter in connectionwith FIGS. 5A-5C. Some embodiments defining a binocular configurationmay include two ports, also referred to herein as “first” and “second”ports, that include similar configurations and provide for similarfunctionalities for first and second respective eyes of a patient, asdescribed in connection with FIGS. 5A-5C, for example.

The apparatus 100 in FIG. 1 also includes a visual tunable lens 110mounted to the housing as part of the port 105. The visual tunable lens110 is designated “visual” because it is possible for the eye 106 to seethrough the visual tunable lens 110. The visual tunable lens 110 is alsoconfigured to focus or defocus light received from the eye 106 to bepassed via an optical path 112 to a wavefront sensor 116, which measuresa wavefront of the light 108 from the eye. The “visual” tunable lens 110is also closer to the eye 106, when the apparatus 100 is in use than anoptional “light source tunable lens” that will be described inconnection with FIG. 2, and which can be a similar tunable lens at adifferent location in the apparatus. In various embodiments, the visualtunable lens 110 mounted in the apparatus such that it is relativelyclose to the eye 106 when the apparatus is brought into proximity withthe eye for examination. A smaller relative separation between thetunable lens and the eye can result in the tunable being smaller andless expensive than would otherwise be needed.

The visual tunable lens 110 has a focal length f and an optical powerP=1/f that are variable. In some embodiments, the visual tunable lens110 is configured to apply a variable spherical power (focus/defocus) tothe light 108 from the eye. In other embodiments, the visual tunablelens 110 can also apply astigmatic power (cylinder) and also vary axisof the cylindrical (astigmatic) power applied to the light. In someembodiments, the visual tunable lens can be configured to apply variablespherical and astigmatic optical powers, as well as apply axisorientation for the astigmatic power, mutually independently. In someembodiments, the visual tunable lens 110 is further configured to applya spherical equivalent power, vertical Jackson cross cylinder, andoblique Jackson cross cylinder mutually independently.

It should be understood that any “tunable lens,” as used herein, caninclude a plurality of individual tunable lenses arranged (opticallystacked) in series, along the same optical axis, for example. Individualtunable lenses can be stacked in series (along the same optical axis) inorder to increase the range of lens powers that can be simulated by thesystem. Stacking of tunable lenses may also improve the dynamic range orreduce the overall aberrations of the system. For example, a visualtunable lens may include a first individual tunable lens with a widerange of coarse tunability for a given optical correction such assphere, as well as a second individual tunable lens with a narrow rangeof fine tunability for the given optical correction. Further, theoptional mutual independence of spherical and astigmatic powers withvariable axis may be achieved by applying the powers and axis usingrespective individual tunable lenses. This same method of usingindividual tunable lenses can be used to apply spherical equivalentpower, vertical Jackson cross cylinder, and oblique Jackson crosscylinder mutually independently.

In some embodiments, the visual tunable lens 110 can be at least one ofa liquid-filled lens, an electro-wetting lens, an Alvarez lens, spatiallight modulator, deformable mirror, a lens with power that variesspatially (e.g., a progressive lens), a multi-lens system that changeslens distances to tune optical power (e.g., optical trombone, Badalsystem), or a tunable Fresnel lens. In some embodiments, the visualtunable lens can include a two-element object configured to apply thevariable focal power as a function of lateral or rotational displacementof the two elements with respect to each other. For example, an Alvarezlens pair can include two such optical elements configured to belaterally displaced with respect to each other, in a directionperpendicular to an optical axis of the elements, to apply the variablefocal power. Another embodiment includes a lens that is tunable byvirtue of being asymmetrical having different focal powers alongdifferent points on the lens. Such an asymmetrical lens can be displacedalong a plane perpendicular to an optical axis of the system in order tovary the focal power of the lens. Asymmetrical lenses of this type havebeen termed “hybrid Fresnel lenses” and have been used in virtualreality headsets, for example.

Example tunable lenses that can be used in embodiments described hereincan include, for example, the Optotune® EL-10-30 series of liquid-filledtunable lenses. This series has focal lengths and corresponding opticalpowers that can be tuned within milliseconds, providing fast responsefor iterative wavefront measurements performed in a closed loop fashion,as further described hereinafter. One model of the Optotune® EL-10-30can be tuned between +8.3 and +20 diopters (dpt) of optical power,corresponding to +120 to +50 mm in focal length, for example.Furthermore, the Optotune® EL-10-30 series is available withnear-infrared (NIR) optimization, which is useful for detecting NIRlight received from the eye, as is preferably done in some embodiments.Tunable lenses can also cover negative power ranges to be used withmyopic patients. The Optotune® EL-10-30-C-NIR-LD-MV, for example, can betuned between −1.5 and +3.5 dpt. Another example tunable lens that canbe used includes the Varioptic Visayan® 80S0 electro-wetting tunablelens, which can apply variable focus (−12 to +12) and astigmatism (−6 to+0 dpt) powers.

In FIG. 1, the visual tunable lens 110 is also configured to pass thelight 108 from the eye along the optical path 112 toward the wavefrontsensor 116. The wavefront sensor 116 is configured to receive the lightfrom the eye and to measure a wavefront 114 of the light 108 from theeye. The wavefront sensor 116 can be, for example, a Hartmann-Shackwavefront sensor comprising an array of lenslets having the same focallength and configured to focus light received, at various points in across-section of a beam of light, onto a photon sensor, which can be aCCD or CMOS array, for example. As is known and understood in the art ofwavefront sensing, such a wavefront sensor produces a pattern of spots,from which a wavefront of the light being measured can be determinedwith high precision.

The wavefront sensor 116 provides a representation 118 of the wavefrontof the light 108 to a determination module 120. The representation 118of the wavefront can include, for example, an image in the form of pixelvalues for a sensor array of the wavefront sensor 116. However, in otherembodiments, the wavefront sensor 116 can be configured to provide therepresentation 118 in other forms, such as a compressed image or aseries of spot separations or spot center positions on the sensor array,for example.

The determination module 120 is configured to determine a property 122of the eye 106 based on the measured wavefront from the sensor 116. Theproperty 122 can include an optical property such as one or more valuesfor aberrations of the eye, an eyeglass or contact lens prescription forthe eye, objectively or subjectively determined correction parameters,accommodation amplitude or presbyoptic prescription, lensometer data foreyeglasses worn or intended to be worn by a patient, or other relateddata. Moreover, in some embodiments, the determination module 120 can beconfigured to output other data, such as a spot pattern produced by thewavefront sensor 116. Such spot patterns can be used advantageously insome embodiments to provide live images for alignment of the eye andother purposes, as described further hereinafter.

In some embodiments, the housing 102 is configured to be gripped by atleast one hand of the person having the eye 106 to support a full weightof the apparatus during use. An example of such a configuration isincluded in FIGS. 5A-5C, for example. These embodiments can enable aperson having the eye to use the apparatus 100 portably, even in theabsence of a doctor, operator, or other assistance to obtain eye datasuch as a prescription for eyeglasses.

In some embodiments, the port 105 can include an optical window in thehousing 102 or can be an opening in a modular attachment to the housing.In some embodiments, the eyecup 104, the visual tunable lens 110, andthe port 105 can be physically separate. In some embodiments, port 105can be described as a “proximal” port, and an additional “distal” portcan also be provided in the housing, such that the device is “openview,” enabling the eye 106 to see all the way through the apparatus 100to an object or feature external to the apparatus 100. The apparatus 100is monocular, in the sense that it is configured to receive one eye.However, in other embodiments, an apparatus can be binocular, asdescribed hereinafter in connection with FIGS. 5A-5C, for example. Insome binocular configurations, a second visual tunable lens can beconfigured to be mounted to the housing and to apply a variable focalpower to light from the second eye. The second visual tunable lens canperform functions similar to those of the first visual tunable lens 110,or separate functions, as will be described further hereinafter.

In some embodiments, an apparatus can include a visual tunable lensconfigured to be adjusted iteratively to optimize the wavefront 114. Forexample, the visual tunable lens 110 can be adjusted to make thewavefront 114 as close as possible to a plane wavefront, such thataberrations produced by the eye 106 can be minimized, and the visualtunable lens 110 can simulate an eyeglass lens worn by a person havingthe eye 106.

In some embodiments, the eye 106 is a living eye of a person. However,in other embodiments, the eye 106 is an artificial eye that can be usedfor calibration purposes, for example, or for determining theprescription of a pair of eyeglasses in accordance with lensometerfunctions, as further described hereinafter in connection with FIGS.5A-5C.

FIG. 2 is a schematic block diagram illustrating an embodiment apparatus200 that is configured to be open view and also include other optionalfeatures. Open view embodiments have the advantage that the eye 106 canview target indicia external to, and spaced away from, a housing 202 ofthe apparatus 200 through a visual channel between two sides of theapparatus, as further described hereinafter. Provided an external targetobject 252 at a distant external surface 250, or other target indicia,are spaced away from the eye 106 at effective infinity (greater than orequal to 20 feet from the eye), the eye 106 can remain substantiallyunaccommodated and relaxed, such that refractive measurements performedby the apparatus 200 can be improved. It has been shown that wavefrontaberrometry with a closed view configuration induces more instrumentmyopia (0.3 dpt) compared to an open view system (e.g., A. Cervino etal., Journal of Refractive Surgery, 2006).

The apparatus 200 is configured to have the visual tunable lens 110mounted within close proximity to an eyepiece 205 serving as a proximalport configured to receive the light 108 from the eye 106 through thehousing 202. The eyepiece 205 is detachable from the housing 202, suchthat it is modular and can allow the housing 202 to receive othermodular attachments. Example modular attachments can include alensometer attachment, as described hereinafter in connection with FIGS.5A-5C, a calibration attachment, as described hereinafter in connectionwith FIGS. 5D-5K, or other eyepieces having different focal ranges.

As is known, different eyes can have widely varying optical aberrationsand require widely varying prescriptions. A given visual tunable lenshaving a given tunability range, such as the Varioptic Visayan® 80S0tunable lens described hereinabove, which has an adjustment range from−12 to +12 dpt, will be able to simulate eyeglass corrections forpatients having a given range of needed correction. Thus, in someembodiments, the eyepiece 205 with the visual tunable lens 110 coveringone range of corrections can be modularly replaced with another eyepiecehaving a different tunable lens covering a different range ofcorrections to address patients having a correspondingly different rangeof correction.

Alternatively, in some embodiments, the eyepiece 205 is configured toaccommodate additional lenses and optics for various purposes. Forexample, the eyepiece 205 can be configured to accommodate a fixed lens,also attached to the housing, to apply a fixed focal power to the light108 from the eye to shift a range of refractive correction measurementof the apparatus 200. Furthermore, a variety of fixed lenses havingvarious fixed focal powers can be alternately received by the eyepiece205, or by another portion of the housing 202, or inside the apparatus200, for example, to address different persons with different refractivecorrections. Furthermore, the eyepiece 205 can also be configured toaccommodate a fogging lens or optic configured to fog the view of theeye through the apparatus 200. Fogging has the advantage that it is anon-cycloplegic (does not require cycloplegia) approach and also avoidsthe need for an open view system. Fogging can also be modified accordingto a given patient's type of refractive error (myopia or hyperopia).

Still further, the eyepiece 205 can be configured to accommodate avisual tunable lens that comprises a series of individual tunable lensesas described hereinabove in relation to FIG. 1. Using a series ofindividual tunable lenses instead of a single visual tunable lens, forexample, may increase the range of lens powers that can be simulated bythe system. A series of individual tunable lenses may also improve thedynamic range or reduce the overall optical aberrations of the system.The individual tunable lenses may be arranged (stacked) optically inseries with each other, all centered on a common optical axis, forexample. The individual tunable lenses may be used to cover separatelarger and smaller optical correction ranges, for example. Further,individual tunable lenses in such an arrangement (stack) may beconfigured to address, separately, different respective opticalcorrections. A series of individual tunable lenses can separatelyaddress spherical power, astigmatic power (cylinder), axis of thecylindrical (astigmatic) power applied to the light, and evenaberrations of higher optical order mutually independently, for example.In some embodiments, the series of individual tunable lenses can beconfigured to apply a spherical equivalent power, vertical Jackson crosscylinder, oblique Jackson cross cylinder, and higher-order correctionsmutually independently.

As is understood in the science of refractive care, corrective lenses ofeyeglasses are typically situated about 14 mm from the surface of thecornea of a patient's eye. In preferred embodiments, in order to bestsimulate refractive correction of eyeglasses, the visual tunable lens110 is configured such that a plane 228 of the lens 110 is configured tobe a distance 229 of about 14 mm from a front surface 227 of the cornea.Thus, the plane 228 at which the visual tunable lens 110 is situated, inthis case, corresponds to the spectacle plane for the eye 106 when theproximal port has received the eye.

While a refractive measurement is being performed, the eye 106 can seelight 248 from the external target object 252 located on the surface 250at effective infinity. This open view design is facilitated by two beamsplitters 226 a and 226 b that perform various functions within theapparatus and are also largely transparent in the visible spectrumperceived by the eye 106.

The beam splitter 226 a is configured to reflect NIR light 108 receivedfrom the eye 106 toward the wavefront sensor 116. The optical pathbetween the beam splitter 226 a and the wavefront sensor 116 alsoincludes various conditioning optics 236 a. The conditioning optics 236a can include, for example, a beam aperture/iris, a narrowband opticalfilter configured to pass only NIR light of a given wavelength, anattenuation filter, etc. The conditioning optics 236 a can alsooptionally include cross-polarizers disposed in the optical path andconfigured to minimize unwanted light at the wavefront sensor 116. Inthe case of a beam aperture, light from the eye illumination lightsource can be restricted by the aperture, and example aperture sizes mayrange between about 50 μm and about 500 μm.

The wavefront sensor 116 provides the wavefront representation 118 to adetermination and control module 220, which is configured to determinethe property 122 of the eye. The determination and control module 220performs functions similar to those of determination module 120 in FIG.1, but the module 220 also includes control functions. In particular,the control module 220 outputs a control signal 230 a to a lens driver232 a, which outputs a drive signal 234 a to the visual tunable lens 110to set the lens 110 to the appropriate focal power. With appropriatelogic in the determination and control module 220, this forms aclosed-loop system (circuit), wherein the wavefront representation 118can be continuously monitored, and wherein the control module 220 canprovide appropriate control signals 230 a to update the setting of thevisual tunable lens 110 continuously. This process can be iterative tominimize wavefront errors of the eye 106 using the visual tunable lens110. In this manner, the variable focal power of the visual tunable lensmay be adjusted iteratively in response to successive wavefrontmeasurements in order to minimize a wavefront error of the light fromthe eye. Various iterative processes are further described hereinafterin connection with FIGS. 6 and 10A-10B, for example.

The apparatus 200 also includes an illumination light source 238 that isconfigured to output NIR light (eye illumination light 240) toward theeye. In other embodiments, the eye illumination light and light receivedfrom the eye may be visible or infrared. The illumination light 240 isreflected by the beam splitter 226 b, passes through the beam splitter226 a, and exits the proximal port 205 through the visual tunable lens110 to enter the eye 106. The light 240 is intended to form a focusedspot 207 at the retina of the eye 106. A portion of the eye illuminationlight 240 is reflected and scattered by the eye 106 and is received aslight 108 from the eye to be detected at the wavefront sensor 116.

When the eye illumination light 240 passes through the visual tunablelens 110, its convergence or divergence is affected by the setting ofthe tunable lens 110. In order to maintain a focused spot 207 at theretina, the apparatus 200 includes a light source tunable lens 200 thatapplies variable focal power to the eye illumination light 240 tomaintain the focused spot 207 at the retina. Thus, when thedetermination and control module 220 adjusts the focal power of thevisual tunable lens 110, the light source tunable lens 210 can beadjusted to a corresponding value that affects only the eye illuminationlight 240 and maintains the focused spot 207. As will be understood bythose skilled in the art of optics, the corresponding settings betweenthe visual tunable lens and the light source tunable lens 210 can bepre-calibrated such that an appropriate setting for the lens 210 can beknown for every setting of the tunable lens 110. In order to make thesecorresponding adjustments, the determination and control module 220 canstore calibration data or receive the calibration data from anothersource, such as memory illustrated in FIG. 4, to make the appropriatecorresponding settings.

In cases in which the visual tunable lens 110 can correct over therefractive error range needed for a given patient, correspondingadjustments to the light source tunable lens 210 may not be required.However, the light source tunable lens 210 can be used to extend therange of measurement for a given visual tunable lens 110 by reducingspot size of illumination light focused onto the retina of the eye,particularly in case the eye has a refractive error greater in magnitudethan the maximum refractive error that can be corrected with the visualtunable lens 110. Furthermore, the light source tunable lens 110 can beused to expedite analysis of a patient's eye and determination of acorresponding prescription by sweeping the range before, during, orafter tuning the visual tunable lens. For example, if a particularvisual tunable lens cannot be tuned as fast as desired for a given setof refractive measurements, then the optical power of the light sourcetunable lens may be adjusted, in parallel with the optical power of thevisual tunable lens, to achieve a particular combined power setting morequickly. Moreover, the light source tunable lens 210 can be used toreduce speckle, as described further hereinafter.

In order to control the light source tunable lens 210 in FIG. 2, thedetermination and control module 220 outputs a control signal 230 b to alens driver 232 b. The driver 232 b outputs a drive signal 234 b to thelight source tunable lens 210 to make the appropriate setting.Preferably, where the visual tunable lens 110 controls sphere, cylinder,and axis independently, the light source tunable lens 210 includessimilar, independent adjustments such that the eye illumination lightcan remain focused on the retina for all visual tunable lens settings.

The optical path between the illumination light source 238 and the beamsplitter 226 b also includes conditioning optics 236 b. The optics 236 bcan include some functions similar to those of the conditioning optics236 a. For example, the optics 236 b can include a narrowband filterconfigured to pass only light of wavelengths corresponding to theillumination light source 238. The optics 236 b can also include an iris(aperture) configured to adjust diameter of the eye illumination light240 or a diaphragm to define the illumination light and to align thelight 240 with the beam splitter 226 b. The illumination light source238 can be a light emitting diode (LED), but it can also be a diodelaser or other collimated, coherent (or semi-coherent, such as asuperluminescent diode) light source, for example.

As will be understood by those skilled in the art of optics, a coherentillumination light source 238, such as a laser, can produce some degreeof speckle pattern at the eye 106 and at the wavefront sensor 116,depending on the degree of coherence of the light source 238. Randomspeckle patterns with high contrast may, therefore, be present in a spotdiagram produced using the wavefront sensor. These speckle patterns caninterfere with the ability of the wavefront sensor 116 to distinguishsensitively between laser speckle and the spot pattern that defines thewavefront of the light 108. Speckle contrast can reduce the accuracy oflocalizing each spot in a detected spot diagram, which, in, turn canreduce the accuracy of a wavefront that is reconstructed using thedetected spot diagram.

One advantage of embodiments is that the determination and controlmodule 220 can be configured to dither (i.e., rapidly apply variablefocal power or adjust another refractive setting of) either the visualtunable lens 110, the light source tunable lens 210, or both tunablelenses slightly while spot diagrams are being acquired by the wavefrontsensor. In the case of the light source tunable lens being dithered,variable focal power is applied to the light 241 from the light source210. This dithering can randomize the speckle pattern produced by theeye illumination light 240 at the eye 106, or, equivalently, randomize aspeckle pattern produced by the light 108 from the eye at the wavefrontsensor 116. This dithering, as described in connection with FIG. 9B, forexample, can introduce small variations into the wavefront of the lightto randomize the speckle pattern generated at the eye by an eyeillumination light source and received at the wavefront sensor.

Such dithering can reduce or eliminate the effects of laser specklepattern that would otherwise diminish measurement sensitivity of thewavefront sensor 116. If the magnitude of the dithering is sufficientlylarge, the speckle pattern will be randomized over the course of anacquisition. If the speckle pattern is sufficiently randomized over thecourse of a single exposure, an averaged-out speckle pattern will becaptured. This implies that the spots in the spot diagram can be moreaccurately localized due to the reduced speckle contrast. Furthermore, adithering magnitude that is sufficiently large to randomize the specklepattern can also be small enough to have no appreciable impact on thesize of the focal spot 207 or the accuracy of the wavefrontmeasurements. An example spherical dithering magnitude includes, forexample, +/−0.01 dpt. However, other example spherical ditheringmagnitudes are much greater, such as in a range of 0.25-0.5 dpt, forexample. Other tunable lens parameters, such as cylinder power, axis,higher order parameters, or parameters such as spherical equivalentpower in other known basis sets, for example, may be dithered as analternative to, or in addition to, dithering sphere. Thus, the abilityto eliminate or reduce laser speckle noise is yet another advantage oftunable lenses used in embodiment apparatus and methods.

The apparatus 200 also includes an optional target light source 244mounted to the housing 202. FIG. 2 illustrates the target light sourcemounted inside the housing 202, but other embodiments can includeoutside mounting. The target light source 244 is configured to outputvisible target light 246, which is reflected by the beam splitter 226 band output from the apparatus 200 through a distal port 224 in thehousing. Together, the proximal and distal ports form a visual channelparallel to the optical axis 242 through which the eye 106 can see theexternal target 252. The visible target light 246 creates a spot orother indicia on the distant external surface 250 external to and spacedaway from the housing 202. The spot or other indicia can be viewed bythe eye 106 to cause the eye to be unaccommodated, with the distantexternal surface 250 at effective infinity from the eye. The visibletarget light 246 is reflected or scattered from the surface 250, and aportion returns to the eye 106 as return light 248 through the apparatus200. However, in other embodiments, the target light source 244 is notused. Instead, the return light 248 viewed by the eye 106 is ambientlight scattered or reflected from the external target object 252 andthrough the apparatus 200.

In the schematic block diagram illustrated in FIG. 2, the light 108 fromthe eye, visible target light 246, return light 248, and eyeillumination light 240 are shown as being offset from the optical axis242 of the eye. This depiction is for convenience in illustration only,and all of these light beams can be mutually coincident, collinear, andcentered on the optical axis 242.

However, in preferred embodiments, the eye illumination light 240exiting the port 205, and the light 108 from the eye entering the portand received by the tunable lens 110, are non-collinear. Thisnon-collinear orientation can reduce or eliminate eye illumination light240 that is back-reflected from the surface of the cornea of the eyefrom being received at the wavefront sensor. This can be very helpful inreducing noise and increasing signal-to-noise ratio for wavefrontsignals detected by the wavefront sensor.

In conformity with the principle of making the light entering the eyenon-collinear with the light exiting the eye, various adjustments can bemade to the optical configuration in FIG. 2. For example, a detectionplane 217 of the wavefront sensor 116 can be non-perpendicular to anillumination axis 241 of the illumination light source 238. Thewavefront sensor 116 can be slightly non-parallel with the optical axis242 of the eye. In other words, the detection plane 217 of the wavefrontsensor can be non-parallel with an illumination axis of the eyeillumination light 240 within an optical path between the beam splitter226 b and the eye 106, and the detection plane 217 can benon-perpendicular with an axis of illumination of the eye illuminationlight 240 within an optical path between the eye illumination lightsource 238 and the beamsplitter 226 b.

FIG. 3 is a schematic diagram illustrating various optional input andoutput features of embodiment devices, such as those illustrated inFIGS. 1 and 2. In particular, the housing 202 of the apparatus 200illustrated in FIG. 2 can include a reporting interface screen 354, adial 356, a communication interface 360, directional buttons 358, and atrigger switch 397. The dial, directional buttons, and trigger switchare examples of manual controls that can be configured to be adjustableby an eye patient, or by a clinician, to adjust the variable focal powerof the visual tunable lens in accordance with a subjective refractivepreference of the eye patient. In other embodiments, these inputs andoutputs are provided by peripheral devices in operational communicationwith the apparatus 200. Examples of peripheral devices, can include acellular phone, as illustrated in FIG. 4, or a separate, handheld, wiredor wirelessly connected controller that a clinician, patient or otheruser can use to specify inputs or receive outputs, for example.

The reporting interface 354 can be an LCD screen, for example, on thehousing 202 that can be read by a user to obtain a prescription foreyeglasses, as illustrated, or another property of the eye 106. Thereporting interface screen 354 provides sphere (S), cylinder (C), andaxis (A) measurements for right (OD) and left (OS) eyes aftermeasurements are completed. Various other information can also bepresented to a user or operator using the reporting interface screen354, such as information about higher order aberrations, Zernikepolynomial parameters measured for the right and left eyes, a contactlens prescription, alignment information, and other information. Asanother example, the reporting interface screen 354 can show a liveimage produced by the wavefront sensor 116 in FIG. 2 to assist withcalibration of the apparatus or for eye alignment purposes for initialsetup, for example. Further alternative information that can be providedby the reporting interface screen 354 includes static images produced bythe wavefront sensor 116, other information representative of thewavefront detected, calibration instructions, operating instructions,etc. Furthermore, in some embodiments, the reporting interface screen354 is a touchscreen enabling a user to input information, such asselecting a measurement to be performed. Actual placement of thefeatures shown in FIG. 3 onto a device housing or peripheral module mayvary in various embodiments. An example placement of the trigger switch397 is illustrated in FIGS. 5A-5C.

The communication interface 360 includes a speaker 362 configured toprovide audible instructions to a user, such as instructions for how toalign the eye to an input port of the housing for best measurementaccuracy. In some embodiments, the speaker 362 provides step-by-stepinstructions to the user before and during a measurement of the eye. Theinterface 360 also includes a microphone 364 that can be used to receiveinputs from the user, such as a refractive preference of the user. Thisfeature is particularly useful when the apparatus 200 operates inphoropter mode, as will be described further hereinafter in connectionwith FIGS. 8A-8B, for example. Thus, the speaker 362 can provide certaininstructions such as “tell me which lens setting is best, one or two.”The apparatus 200 illustrated in FIG. 2 can then set the visual tunablelens to two different settings, one subsequent to the other, and thespeaker 362 can indicate which setting is 1 in which setting is 2. Auser can then speak, through the microphone 364, “one” or “two” toindicate which setting of the visual tunable lens 110, simulating aneyeglass correction, is preferable to the user, who is the person whoseeye 106 is being measured.

As an alternative to the verbal communication just described forspecifying subjective preferences, the directional buttons 358 can bepressed by a user to specify which visual tunable lens 110 setting ispreferable. For example, the wavefront sensor 116 can be used todetermine an objective refractive correction for the user. The visualtunable lens 110 can then be set to simulate a corrective lens appliedto the eye 106. The user can then be given the opportunity to specifyvarious changes to refractive settings of the visual tunable lens 110,using the directional buttons 358, in accordance with a subjectivepreference. This range of adjustment can be a fine adjustment over arelatively small range, such as a spherical correction adjustment rangeof +/−0.25-0.50 dpt. Once the user has specified spherical correction tothe subjective preference, the buttons 358 can then be used to optimizecylinder and axis in turn according to subjective preferences, in asimilar fashion. After the visual tunable lens 110 is set to all thepreferred settings for sphere, cylinder, and axis, the process can berepeated iteratively for greater precision or to evaluate repeatabilityof subjective preference settings.

The dial 356 can be used as an alternative to the directional buttons358. For example, the user can turn the dial 356 to adjust the sphericalcorrection over the limited range of +/−0.25 dpt or +/−0.50 dpt, forexample. The dial 356 can be preferable to the directional buttons 358since rotational motion of the dial 356 can be smoother and cause lessdisturbance to the housing 202 than pressing buttons. The dial 356 mayalso be easier to use for other reasons, such as the user's ability toturn the dial 356 quickly or slowly, in accordance with the user'spreference and the degree of adjustment required.

The trigger switch 397 provides another means of input by the user tothe apparatus. In particular, as further described hereinafter inconnection with FIG. 5A and FIGS. 8A-8B, for example, the trigger switch397 can be pressed by the user when the user is ready for a measurementto occur, and then the user can release the trigger switch 397 once asimulated refractive correction provided by the visual tunable lens 110operating in closed-loop fashion with the wavefront sensor is completelysatisfactory. An example location for the trigger switch 397 is shown onthe embodiment device illustrated in FIG. 5A.

FIG. 4 is a computer interconnect diagram illustrating variouscomponents of the determination and control module 220 in FIG. 2 and itsconnections to various components, including some internal componentsshown in FIG. 2 and other optional components shown in FIG. 3, as wellas some other optional components that are not illustrated in FIGS. 2-3.In the apparatus embodiment illustrated in FIG. 2, the determination andcontrol module 220 performs all necessary computing and controlfunctions for the apparatus 200. It should be noted that in otherembodiments, these functions can be distributed between a determinationand control module and other processors or controllers, as will beunderstood by those skilled in electrical and computer engineering.

The determination and control module 220 includes a computer bus 466used as an interconnect for various components. The module 220 includesmemory 470 and a processor 472 that are used to store data and programinstructions and perform necessary processing functions, processingfunctions can include determining the property of the eye, such asoptical properties including a refractive correction prescription to beapplied to the eye, based on the measured wavefront, the tunable lenssetting, and any objective preference information obtained. Therepresentations 118 of the wavefront entering the module 220 in FIG. 2can be stored in the memory 470 for analysis by the processor 472. Themodule 220 also includes a network interface 468 coupled to the computerbus 466 for communicating with outside computers or networks ifdesirable. The network interface 468 can be used to report refractiveresults to an external computer or network for eyeglass orderingpurposes, for example, or allow the functioning of the apparatus 200 tobe monitored by an external or even remote computer, for example.

The processor 472 is coupled to a visual tunable lens interface 474 athat controls the driver 232 a illustrated in FIG. 2. Thus, through thevisual tunable lens interface 474 a, the processor 472 can control thesettings for the visual tunable lens 110. In a similar fashion, theprocessor 472 is coupled to a light source tunable lens interface 474 bfor control of the light source tunable lens 210 illustrated in FIG. 2.It should be understood that, where either the visual tunable lens 110or the light source tunable lens 210 includes a series of individualtunable lenses, as described hereinabove in relation to FIG. 1, eitherinterface 474 a or 474 b may correspondingly include a series ofindividual interfaces for mutually independent control of therespective, individual tunable lenses.

The module 220 also includes interfaces 476 a and 476 b to control theconditioning optics 236 a and 236 b, respectively. The interfaces 476a-b are particularly useful in cases in which the conditioning opticsare adjustable. For example, the conditioning optics 236 a-b can includesuch features as variable attenuation and adjustable diaphragms andirises for beam conditioning.

The module 220 also includes a wavefront sensor interface 478 forreceiving data from the wavefront sensor 116 in FIG. 2. A communicationinterface 480 in the module 220 allows the module 220 to communicatedata to and from the communication interface 360 illustrated in FIG. 3.While not shown in FIG. 4, other interfaces can be provided in thedetermination and control module 220 for sending data to, and receivingdata from, the reporting interface screen 354, dial 356, directionalbuttons 358, and trigger switch 397, which are illustrated in FIG. 3.Interfaces 482 and 484 are also included in the module 220 forcontrolling the illumination light source 238 and the target lightsource 244, respectively, which are illustrated in FIG. 2. For example,these light sources may be turned off when not in use, and theirintensity may also be adjustable in certain embodiments.

The network interface 468 can include a wired or wireless interface,such as a universal serial bus (USB) interface, a wired Ethernetinterface, a bluetooth communication module, a wireless infrared (IR)interface, a wireless local area network (WLAN) interface, or a wirelesscellular data interface. Through such example interfaces, the processor472 can communicate with an external or remote device that is outfittedwith a similar communication interface. Such an interface can be used toprint eye measurement results, store results on a thumb drive or otherstorage medium, send measurement results to a personal computer,cellular phone, smart phone, or cloud-based server, send prescriptionorders for eyeglass or contact lens prescriptions via any of these orother known means, communicate in other ways, or provide other outputdata. In one example, objective refraction results, subjectiverefraction results, lensometry results, accommodation measurements,another eye property, machine learning results, or a combinationthereof, as determined by any one or more of the procedures illustratedin FIGS. 7, 8, 9A, 9C-9F, and 10A-10B, may be communicated directly orindirectly to a desired location or device with the network interface468 being configured appropriately.

One or more of the interfaces illustrated in FIG. 4 can be replaced orhave its functions augmented by a suitably programmed device, such as anoptional field-programmable gate array (FPGA) 486 or a digital signalprocessor (DSP) 488. Furthermore, an application-specific integratedcircuit (ASIC) 490 or programmable logic device (PLD) 492 can also beused.

As also illustrated in FIG. 4, the module 220 can include an interfaceused to communicate with a cellular phone 492. In some embodiments, thecellular phone can be configured to be attached to the housing 202 orcan be otherwise programmed to perform some of the functions describedin connection with FIG. 2 for the determination and control module 220.Furthermore, in some embodiments, the cellular phone 492 is used todisplay a representation of the wavefront of the light from the eye.Such a representation can be used for alignment of the eye to theapparatus 200 or for other subjective or objective analytical purposes,for example. In some embodiments, the cellular phone 492 can be used toperform the functions of the reporting interface screen 354 shown inFIG. 3, as well as other input or output functions of the dial 356,communication interface 360, directional buttons 358, or trigger switch397. Furthermore, in some embodiments, the cellular phone can be used asa Hartmann-Shack wavefront sensor. For example, a standard multi-pixelsensor array on the cellular phone that is used to acquire photographscan be adapted to perform the functions of the light sensor array of theHartmann-Shack wavefront sensor, and a separate lenslet array can beused to focus the light 108 received from the eye onto the sensor array.In some embodiments, the cellular phone includes two multi-pixel sensorarrays that are used as respective Hartmann-Shack wavefront sensors forrespective eyes of a patient. Further, a first one of the two sensorarrays may be used as a wavefront sensor, while a second one of the twosensor arrays may be used to perform one or more of pupil measurements,keratometry, iris imaging, or other known ophthalmic imaging functions.

FIG. 5A is a top-view illustration of an embodiment, binocular,wavefront aberrometer apparatus 500. The apparatus 500 is particularlyconfigured to enable not only wavefront aberrometer measurements usingthe visual tunable lens 110 as illustrated in FIG. 2, but also to enablelensometer measurement functions. The apparatus 500 includes a housing502, which includes grip features 503 configured to be gripped by atleast one hand of a person having the eye 106 to support a full weightof the apparatus 500 during use.

Connected to the housing 502 is an eyecup 504 configured to providemechanical registration of the apparatus 500 against a forehead andcheek of a person (user, patient) having the eye 106. A port 505 in thehousing is configured to receive the eye 106 and to receive light fromthe eye, as described in connection with FIG. 2. The trigger switch 397is mounted to the housing 502 as illustrated in FIG. 5A. The switch 397performs the functions as described in connection with FIG. 3. Inparticular, when a user is ready for the apparatus 500 to perform ameasurement, the user presses the trigger switch 397. After the triggerswitch is pressed, successive wavefront measurements are obtained by thewavefront sensor 116 illustrated in FIG. 2, and the determination andcontrol module 220 adjusts the visual tunable lens 110 to simulateeyeglass correction.

Each time the visual tunable lens 110 is adjusted, the light sourcetunable lens 210 can be adjusted by a compensating amount to cause theeye illumination light 240 to form a focused spot 207 at the retina ofthe eye 106. These adjustments can be performed iteratively, as furtherillustrated hereinafter in connection with FIG. 6, until the user issatisfied with the simulated refractive correction. Once the user issatisfied, the user can again press the trigger switch 397 to indicatethat the correction is satisfactory. In other embodiments, the user or atechnician or other person assisting can press and hold a trigger switchwhile iterative adjustments are performed, and release of the triggerswitch can indicate that a user is satisfied with the correction.

The apparatus 500 also includes reporting screen 554 that is configuredto display a lens prescription intended for the patient (user). Invarious embodiments, the reporting screen 554 can be configured todisplay a contact lens prescription, a wavefront spot pattern foralignment or other purposes, or other information described inconnection with the reporting interface screen 354 illustrated in FIG.3, for example.

FIG. 5A also shows a lensometer attachment 591, modularly attached tothe apparatus 500 via a modular interface 592, for performing lensometermeasurements for eyeglasses 598. The housing 502 is thus configured toreceive a lensometer attachment 591 that is configured to receive andsupport a corrective lens intended to be worn by a person. Thelensometer attachment 591 can also be configured to support a lens blankthat is intended to be manufactured into a corrective lens; in this way,the lensometer attachment 591 is useful for both lensometer measurementsin a clinical setting and for analysis of lenses and lens blanks duringa lens manufacturing process. The wavefront sensor can measure thewavefront of the light received through the corrective lens or lensblank. A determination module, such as module 120 in FIG. 1 or module220 in FIG. 2, can be configured to determine a refractive property ofthe corrective lens or lens blank based on a lens wavefront of lightreceived through the corrective lens or lens blank.

In FIG. 5A, the lensometer attachment 591 includes lens holding bays 594for placement of the pair of eyeglasses 598, with each lens in its ownisolated bay. A calibration reservoir 595 including artificial eyes(model eyes) 599 is also included in the attachment 591 for aligning twooptical components of known optical wavefront properties to tworespective optical channels in the apparatus 500. The calibrationreservoir 595 may also be referred to as calibration holder orcalibration bay.

The attachment 591 in FIG. 5A also includes a sliding track andmechanism 596 between the modular interface 592 and the calibrationreservoir 595 to clamp the optical components of the eyeglasses 598 in amanner to minimize movement and stabilize the eyeglasses for lensometermeasurements. The sliding track and mechanism 596 can be used to set adistance between the two channels of the binocular apparatus 500. Whenthe apparatus 500 is used to determine a refractive correction forsomeone's eye, the sliding track and mechanism 596 can be used to adjustthe binocular apparatus 500 to match the interpupillary distance (i.e.,the distance between the eyes of the user). When the apparatus 500 isused for lensometry on a pair of eyeglasses, then the sliding track andmechanism 596 can be used to match the binocular apparatus 500 to adistance between respective optical centers of the two lenses of theeyeglasses. The trigger switch 397 also causes the apparatus 500 totrigger a lensometer measurement through the initiation of a softwarecalibration sequence.

The artificial eyes 599 are shown included in the calibration reservoir595 for calibration purposes. The artificial eyes 599 can act as knownaberrations so that aberrations due to the eyeglasses can be determined.The lensometer attachment 591 can be similar in some of its internalstructure to a calibration cradle 517 described further hereinafter inconnection with FIGS. 5D-5K. In particular, there can be reservoirs inwhich to hold the artificial eyes and slots in which eyeglass lenses canbe placed.

The tunable lens 110, which is used in the apparatus 500 for eyemeasurement purposes as further described herein, can be optionally usedor removed from the apparatus for lensometer purposes. Where the tunablelens 110 is used, it can be held at a fixed optical power so as to shiftthe measuring range of the apparatus 500 in case the eyeglass lens beingmeasured fall outside the base range of the apparatus.

FIGS. 5B-5C are side-view illustrations of the apparatus 500 illustratedin FIG. 5A. In particular, FIG. 5D shows the eyeglasses 598 outside ofthe lensometer attachment 591, while FIG. 5C shows the eyeglasses 598inserted into the lensometer attachment. These side-view illustrationsalso show that the apparatus 500 includes a second trigger switch 397 atthe bottom side of the housing 502.

It will be noted from FIG. 5A that the apparatus 500 is binocular indesign. In some binocular embodiments, both sides of the apparatus,addressing opposite eyes of a person using the apparatus, are designedto include optical elements similar to those illustrated in FIG. 2. Inthis way, measurements can be obtained for both eyes of a person usingthe apparatus at the same time. Embodiment apparatuses similar to thatdescribed in connection with FIGS. 5A-5C can simplify alignment of botheyes simultaneously with respective sides of the apparatus.

However, in the embodiment illustrated in FIGS. 5A-5C, one side of theapparatus 500 is configured to perform wavefront aberrometrymeasurements of the eye or eyeglass lens placed in front of the port505, while the other side of the apparatus 500 is configured to have thesame light transmission characteristics as the measurement-opticalchannel, but can otherwise be passive and see-through (i.e., open view).This can ensure that the user has a similar view through both eyes,instead of having the view of one eye brighter than the view of theother eye, for example. Thus, in order to perform both measurements onboth eyes using the apparatus 500, the apparatus can be rotated 180° toaddress opposite eyes of a person using the apparatus 500, and oppositelenses of eyeglasses when used in lensometer mode, each eye or eyeglassin turn. Such open-view, binocular embodiments can permit the viewingconditions of both eyes to be similar to each other. This is in contrastto existing small wavefront aberrometers that are neither open view norbinocular, which makes the viewing conditions of the patient's two eyesdifferent, which can negatively affect binocular subjective refraction(natural viewing).

FIG. 5D is a side-view illustration of the calibration cradle 517,referenced hereinabove, which can be used to calibrate the apparatus 500illustrated in FIGS. 5A-5C. The calibration cradle is configured to bemodularly attached to the housing 502, particularly to the eyecup 504 toobtain a reference wavefront measurement for a perfect eye in theabsence of refractive correction from eyeglasses or the aberrations dueto a living eye. An artificial eye assembly 519 can be mechanicallyattached to the calibration cradle 517 to fulfill this purpose.

FIG. 5E is a perspective view of the calibration cradle 517 with theartificial eye assembly 519 attached thereto.

FIGS. 5F-5K are various illustrations of a calibration cradle 517′similar to the calibration cradle 517 illustrated in FIGS. 5E-5F. Thecalibration cradle 517′ is assembled with the artificial eye assembly519. In particular, FIG. 5F is a side-view illustration of the assembly,FIG. 5G is a perspective view of the assembly, and FIG. 5H is anend-view illustration of the cradle 519. FIGS. 5I, 5J and 5K are variousillustrations showing the calibration cradle 517′ attached to theapparatus 500.

Using the calibration cradle 517 or 517′ attached to the apparatus 500,the apparatus 500 can determine a lens wavefront error due to the visualtunable lens alone for calibration purposes. As is known, tunable lensescan have lower optical quality than fixed lenses. Thus, with a livingeye absent, the artificial eye assembly 519 in place with thecalibration cradle 517 or 517′, and the artificial eye assembly 519having known optical characteristics, and preferably characteristics asclose as possible to those of a perfect eye, resulting in no wavefronterror to the assembly 519, any wavefront error that is measured isprincipally due to the visual tunable lens 110.

This contribution of wavefront error due to the visual tunable lens canbe taken into account by a processor, such as the determination andcontrol module illustrated in FIG. 2, in determining actual wavefronterror due to the eye 106. In this way, the optical quality of the visualtunable lens 110 becomes much less important, enabling the device toprovide highly accurate measurements and prescription determinationseven given the presence of the visual tunable lens 110. Thus, even witha visual tunable lens that has lower optical quality than a fixed lens,the processor may determine the actual wavefront error of the eye 106with high precision by taking into account precise contribution of thevisual tunable lens to wavefront error by calibration.

FIG. 6 is a schematic flow diagram illustrating an iterative process forcorrecting wavefront errors due to aberrations of an eye using thevisual tunable lens illustrated in FIGS. 1 and 2 and for simulating theeffects of eyeglasses. Furthermore, where a light source tunable lens isused, as in FIG. 2, compensating adjustments may be made as follows.

A wavefront 614 a is initially measured by the wavefront sensor 116 inFIG. 2, with no optical power applied by the visual tunable lens 110. Anarrow 611 a represents a tunable lens adjustment applied to the visualtunable lens 110 illustrated in FIG. 2. At this point, a corresponding,compensating adjustment can be made to the optical power of the lightsource tunable lens 210 illustrated in FIG. 2 in order to compensate forthe effect of the visual tunable lens 110 adjustment on the eyeillumination light and to maintain the eye illumination light focusedonto a spot on the retina. A wavefront 614 b is then measured by thewavefront sensor 116, which exhibits less wavefront error (lessdeviation from ideal planar wavefront).

Subsequently, an arrow 611 b illustrates application of furtheradjustment to the visual tunable lens 110 to apply a more minoradjustment to simulate a better eyeglass correction, with correspondingadjustment made to the light source tunable lens 210. A wavefront 614 cis then measured by the wavefront sensors 116. In this case, it can beseen that the wavefront 614 c exhibits some over-correction having beenapplied by the visual tunable lens. An arrow 611 c represents furtherminor adjustment to the visual tunable lens 110 to simulate eyeglasscorrection, as the simulation can best be applied using the parametersavailable with a specific visual tunable lens. As previously described,these adjustable parameters can include sphere, cylinder, and axis forparticular tunable lenses. In addition, as tunable lenses continue to bedeveloped and improved, it is expected that particular tunable lenseswill be able to adjust and correct for higher-order corrections as well.In the case of higher-order corrections, similar iterative adjustmentscan be performed. A further, minor, compensating adjustment can be madeto the light source tunable lens 20.

A final wavefront 614 d is measured by the wavefront sensor 116,representing the best wavefront that can be obtained using theparticular visual tunable lens 110, in view of any optical aberrationspresent in the visual tunable lens and in other optical components ofthe system. The schematic flow diagram illustrated in FIG. 6 can includemany more iterations, depending on eye alignment stability, eyeaccommodation, reproducibility of wavefront measurements, potentialaveraging of subsequent wavefront measurements to obtain best estimates,etc. At each successive wavefront error measurement, a minimum (ormaximum) error in wavefront may be determined. One way to characterizewavefront error is by means of a root mean square (rms) wavefrontmeasurement, for example. However, other measures of wavefront error mayalso be used.

Furthermore, the iterative adjustment and measurement processillustrated in FIG. 6 can be applied to multiple parameters of thevisual tunable lens 110 successively. For example, in example methods,the spherical adjustment of the tunable lens can be optimized withrespect to the measured wavefront followed by subsequent optimizationsof cylinder and axis, for example. This process can then be repeated(sphere, cylinder, and axis measured again) for further optimization.Because of the potential speed of adjusting tunable lenses, as describedhereinabove, for updating lens settings, together with the acquisitionspeed for wavefront sensing (e.g., ten frames per second), this processcan proceed very quickly, even when multi-dimensional and iterative.

FIG. 7 is a flow diagram illustrating a procedure 700 for determining aproperty of an eye. The property can include wavefront error produced bythe eye, a refractive prescription for the eye, an accommodation rangemeasurement, a presbyopia measurement, a phoropter measurement, andother measurements as described herein. Embodiment devices describedherein, such as those described in connection with FIGS. 1-5K, may beused to perform the example procedure 700.

At 713 a, a variable focal power is applied to light received from aneye, via a port of a housing configured to receive the eye, using avisual tunable lens. At 713 b, light is passed from the eye along anoptical path. At 713 c, a wavefront of the light from the eye ismeasured, with the light being received via an optical path from theport of the housing.

At 713 d, a property of the eye is determined based on the wavefront ofthe light from the eye. Further details regarding embodiment proceduresencompassed by procedure 700 are described hereinafter.

FIGS. 8A-8B are a flow diagram illustrating an overview procedure 800including various measurements that can be performed on an eye patient,as well as an example clinical examination flow, using the embodimentapparatus illustrated in FIGS. 5A-5C. Because the embodiment apparatusin FIGS. 5A-5C (also referred to herein as the “QuickSee” apparatus) caninclude various features similar to those illustrated in FIGS. 1-4,reference is also made to those figures.

Row 815 a in FIG. 8A indicates operations that can be performed by auser, such as a person whose eyes are being measured using the QuickSeeapparatus. Row 815 b shows operations that can be performed by anoperator, such as a technician, for example. In other embodiments, theactions described in row 815 b can be performed by the user or can beperformed automatically using an embodiment apparatus. Furthermore,other operations can be performed using embodiment devices by the user,an operator, or an optometrist or ophthalmologist, for example. Row 815c shows example actions that can be performed by the QuickSee apparatus.

Column 821 a in FIGS. 8A-8B illustrates operations that can be used toidentify an objective refractive correction. An objective refractivecorrection, as used herein, denotes a measurement that can be performedwithout regard to subjective refractive preferences of the user. Forexample, a refractive correction can be objectively estimated usingembodiment devices based on the wavefront representation 118 obtained bythe wavefront sensor 116 illustrated in FIG. 2, for example. Column 821b illustrates operations that can be used to improve an objectivecorrection estimate by simulating the effect of refractive correction ofeyeglasses by using a tunable lens, such as the visual tunable lens 110illustrated in FIG. 2, for example.

Column 821 c in FIGS. 8A-8B illustrates subjective refraction operationsthat can be performed to improve objective refraction estimates byobtaining feedback from a user regarding lens preferences, for example.This process is normally referred to as phoroptry when performed using astandard phoropter having a variety of fixed lenses in the clinic of anoptometrist, for example. However, advantageously, in accordance withembodiments described herein, phoroptry can be performed usingembodiment devices automatically or semiautomatically by takingadvantage of tunable lenses. Column 821 d illustrates example operationsthat can be performed using embodiment apparatus and methods to obtaineye accommodation range measurements.

In accordance with the objective refraction process described above, at816 a, the user optionally presents existing eyeglasses to an operator(e.g., technician). At 816 b, the operator measures refractive power ofthe user's existing eyeglasses using the lensometer attachment 591further described in connection with FIGS. 5A-5C. In order to performlensometry, at 816 c, the QuickSee apparatus goes into lensometry mode.Following lensometry, at 818, the lensometer attachment 591 is removed,and apparatus 500 goes into refraction mode for objective measurement ofat least one of the user's eyes.

One advantage of using a visual tunable lens for lensometry includes thefact that a measuring range can be easily shifted by implementing afixed tunable lens offset, for example. This is useful in case aparticular eyeglass lens being measured is outside the base range of theapparatus. A further advantage of using a visual tunable lens forlensometry involves measurement accuracy. In particular, similar to theaccuracy advantage described hereinabove for eye wavefront measurementsin the presence of a visual tunable lens, lensometry accuracy can beimproved by setting the visual tunable lens to negate the optical powerof the eyeglass lens being measured so that the detected wavefront is asparallel as possible. As further described hereinabove, when thedetected wavefront is as parallel as possible, then the wavefrontmeasurements themselves can be more accurate, thus leading to moreaccurate lensometry when based on wavefront measurements. In this case,the measured optical power of the eyeglass lens can be determined basedon the combination of the measured wavefront and the optical powerimplemented

At 823, a user having the eye to be measured aligns an embodimentapparatus with an eye or eyes to be measured. The user puts the devicein contact with the user's face and looks through the apparatus at adistant target. The user keeps the user's eyes open, with occasionalblinking. At 825, the operator helps the user with the alignmentprocess. In some embodiment procedures, alignment instructions areprovided by the apparatus, such as through the speaker 362 illustratedin FIG. 3. At 827, as part of the alignment process, the QuickSeeapparatus displays a live preview of spot diagram images provided by thewavefront sensor 116. These images can be shown at a reporting interfacescreen, such as that illustrated in FIG. 3, or at a screen of anattached cellular phone, as described in connection with FIG. 4, forexample.

At 829, the operator confirms that the QuickSee apparatus is alignedwith the eye of the user. In other embodiments, this can be performedautomatically, using feedback from the device itself. Whether alignmentis confirmed manually by the operator or automatic alignment feedback isprovided, alignment analysis can be based on the spot diagram from thewavefront sensor. As the user looks through the apparatus, the degree towhich the user's eye is optically centered with the wavefront sensor canbe analyzed. In particular, this can be done by checking how well thespot diagram is centered on the wavefront image sensor and thenproviding feedback on how to move the device relative to the user's facein order to optically center the user's eye to the wavefront sensor.

At 831, the user can press the trigger switch 397 illustrated in FIG. 5Ato indicate that refractive measurements should begin. Following this,at 833, the QuickSee apparatus begins real-time refractive errormeasurements. Then, at 835, as necessary, externally mounted orremovable lenses can be added as modular attachments to the QuickSeeapparatus to shift a measurement range of the visual tunable lens or tofog the patient's view. The addition of these lenses may be performed bythe operator, for example. As described hereinabove, the exampleVarioptic Visayan® 80S0 tunable lens can apply variable focus opticalpower between −12 and +12 dpt. Therefore, if this lens is used as thevisual tunable lens, and the patient's eye has a spherical error ofabout −12 dpt, for example, then the tunable lens may not provide aconvenient range of adjustment to ensure that optimum refractivecorrection is determined and simulated for the patient. In this examplecase, an additional, externally mounted, +5 dpt fixed lens could beadded to the apparatus and used to shift the measurement range by +5 dptfor measurement and simulated refractive correction. In alternativeembodiments, a different visual tunable lens having a differentmeasurement range could be used.

As described hereinabove in connection with FIG. 2, for example, theeyepiece proximal port 205 can be configured to accept one or moreadditional, modular, fixed lenses as needed. As an alternative, a usermay be given instructions by the QuickSee apparatus, through thereporting interface screen 354 or the speaker 362 illustrated in FIG. 3,for example, to insert specific lenses for offset or fogging.

As to the eyeglass simulation column 821 b, at 837(1), the permanentlyincorporated visual tunable lens 110 illustrated in FIG. 2 is adjustedin order to neutralize refractive error caused by imperfections in theeye 106. This process can be iterative as illustrated in FIG. 6, forexample. When the refractive error is made as close as possible to zero,indicated by plane waves in FIG. 6, and by a uniform, evenly spaced spotdiagram from a Hartmann-Shack wavefront sensor, for example, and thetunable lens 110 is adjusted to achieve such results, then the eye 106views the external target object 252 through the open view apparatus200. Then, the eye 106 is effectively viewing through a corrective lenssimulated by the visual tunable lens 110. This neutralization processcan be completed empirically by running an optimization routine to makethe spot pattern on the wavefront sensor as uniform as possible. Anexample optimization procedure is described hereinafter.

The optimization procedure to make the spot pattern as uniform aspossible can be performed in several ways. One straightforward method isto minimize the root mean squared (rms) error of the wavefront withrespect to an aberration-free wavefront. Examples of other well-knownparameters which may be used in the optimization procedure are thepeak-to-valley (P-V) wavefront aberration or the Strehl ratio, amongothers. Some of these methods are described in the following paper:“Thibos et al, Accuracy and precision of objective refraction fromwavefront aberrations, Journal of Vision 2004 (4), 329-351.” Theoptimization procedure can be performed iteratively using a standardclosed loop control in which the feedback signal (error signal) is givenby any of the aforementioned parameters.

Another possibility to perform the optimization procedure is to maximizethe optical or visual quality. This approach is based on the fact thatmathematically is easy to add to the eye's aberration map that ourdevice is continuously measuring. Using the measured spherical and/orcylindrical wavefront (which simulates the correction) we can thencompute the resulting retinal image using standard methods of Fourieroptics. The curvature of the added wavefront can be systematically oriteratively varied to simulate a through-focus experiment that variesthe optical quality of the eye+lens system over a range. Given asuitable metric of optical quality (such as the Strehl ratio), thiscomputational procedure yields the optimum lens needed to maximizeoptical quality of the corrected eye.

Alternatively, wavefront error optimization can be based on Zernikecoefficients. Zernike coefficients can be obtained in each measurementby the determination and control module 220 and can be used to calculatethe RMS error of the wavefront obtained by the wavefront sensor 116 (orany other parameter of interest). This parameter can be used as errorsignal in a closed loop to adjust the Sphere, Cylinder and Axis in thevisual tunable lens in order to minimize the RMS error. Furthermore, foreach measurement, the iterative process may be performed to calculatethe adjustments to apply to the visual tunable lens 110 based on opticalor visual quality metrics obtained after retinal image qualityestimation.

As a further alternative, the determination and control module 220 maycalculate Zernike coefficients based on the wavefront obtained by thewavefront sensor 116, and spherical, cylinder, and axis adjustments tothe visual tunable lens 110 may be made to compensate for correspondingrefractive error components indicated by the Zernike expansion. Onesimple example method includes causing the tunable lens 110 to correctfor second order Zernike terms (defocus, oblique astigmatism, andvertical astigmatism).

During this process, in each case of adjustment of the visual tunablelens 110, the light source tunable lens 210 can be adjusted by acorresponding amount to maintain a focused spot of the illuminationlight 240 on the retina.

At 837(2), the visual tunable lens 110 can be adjusted to increase orshift the measurement range. The correction objectively determined basedon wavefront measurements can be implemented as a fixed value foreyeglass simulation. Further, this simulation can be implemented as acoarse offset, and then, in the subjective refraction stage, be allowedto vary over a relatively small range, such as +/−1.0 dpt, +/−0.5 dpt,or +/−0.25 dpt, for example, based a user's preferences. At 837(3),during the real-time measurement and iterative neutralization processdescribed above, the visual tunable lens 110 or the light source tunablelens 210 may be adjusted slightly (dithered) to address speckle noise inspot diagrams obtained by the wavefront sensor 116. This process isfurther described hereinabove in connection with FIG. 2.

At 839, with the spot diagram detected by the wavefront sensor 116optimized to be uniform and to indicate minimized refractive error byadjustments of the visual tunable lens 110, the user can view a standardvisual acuity chart, through the open view apparatus, with a simulatedeyeglass provided by the visual tunable lens 110 through which the userviews.

In column 821 c, at 841, the visual tunable lens 110 has already beenset to an optical power to simulate the best estimate for refractivecorrection based on objective refraction, using measurements of thewavefront sensor. With this setting as a starting point, subjectiverefraction is performed, in a manner somewhat similar to phoroptry.However, with the benefit of the visual tunable lens 110, this processcan be performed automatically or semi-automatically, with minimal helpfrom an external technician, or by the user alone, all while the userviews through the same apparatus used for wavefront aberrometry andobjective refraction.

In one embodiment, the speaker 362 provides an audible message to theuser to turn the dial 356. While still viewing the visual acuity chart(e.g., Snellen chart, LogMAR chart, EDTRS chart, or tumbling E chart) oranother target, the user adjusts the dial 356 to optimize the view forthe eye under test, and sphere is adjusted for the visual tunable lens110 in accordance with the dial 356 adjustments. Subsequently, thespeaker 362 asks if the view is optimized. The user responds, throughthe microphone 364, “yes.” Then, the speaker 362 provides a message toagain optimize the view using the dial 356. This time, the cylinderadjustment of the visual tunable lens 110 is made with the user stillviewing the visual acuity chart. After similar adjustments of the dialand a similar confirmation through the speaker and microphone, an axisadjustment can be made similarly. After this process, it may bedesirable to iterate, by once again asking the user to adjust the dial356 to optimize sphere, and so forth.

In another embodiment, the user uses the directional buttons 358 toadjust sphere correction up or down, as desired. In another embodiment,an external technician provides assistance during the subjectiverefractive measurement. For example, the technician can ask the patientwhether the patient sees more clearly with a first tunable lens settingor a second tunable lens setting, and so on, thus guiding the patientthrough an entire subjective measurement process. The technician canperform subjective refraction using the QuickSee apparatus as,essentially, a phoropter. Switching of visual tunable lens settings maybe done by direct input to the device. However, more preferably, inputcan be via a remote device, such as a tablet computer linked to theQuickSee apparatus. In this case, a tablet computer can be operativelyconnected to the QuickSee apparatus much like the cellular phone 492illustrated in FIG. 4, for example. In yet another embodiment, thevisual tunable lens 110 is slowly varied over a limited range, and theuser presses a trigger button similar to the trigger switch 397 when theuser's view is optimized with respect to sphere, cylinder, or axis, forexample.

At 843, a final eyeglass prescription is obtained based on the finalrefractive values obtained from subjective refraction. In someembodiments, data are collected, either by the apparatus 200 itselfwithin the determination and control module 220, or by an externalmonitoring computer connected via the network interface 468 illustratedin FIG. 4. Data regarding the subjective refraction final values, ascompared with the objective refraction values, can be accumulated toproduce statistics for better prediction of final prescription values.

As described hereinabove, one unique feature of embodiment devices isthe ability to perform both objective and subjective refraction usingthe same device. For each patient whose eyes are measured, embodimentapparatus and methods can be used to obtain (i) an initial objectiverefraction, and (ii) a final subjective refraction. For each patient,these two values can be logged to see how different they are.

By accumulating and learning from such data, methods can be implementedto effectively modify the objective measurement initially measured toprovide a more accurate starting point for subjective refraction. Amachine learning approach can take into account not only objective andsubjective refractions measured for each patient, but also any user's(eye patient's) personal information (e.g., age, gender, race), oradditional information (e.g., high-order aberrations measuredobjectively, or retinal image quality calculated from the measurements),to be stored and analyzed according to a machine learning method tofurther improve prediction accuracy.

A useful advantage of embodiments that use this machinelearning/prediction approach is that overall time for an entirerefraction process can be reduced by having a more accurate startingpoint for subjective refraction. It is also possible that, givensufficiently developed prediction routines, that subjective refractionneed not even be performed, and that prediction of subjective correctionmay be done solely on the basis of objective refraction results.

As further described herein, the property of the eye measured by anembodiment apparatus can be an objective property based on the wavefrontmeasurements, without taking into account subjective patient preferencesthat would be reflected in phoroptry results, for example. Adetermination module can be used to predict a subjective refractivepreference of a person having the eye based on the objective property.The determination module can be made to predict the subjectiverefractive preference based further on a demographic or physicalattribute of a patient. Demographic attributes can include age, gender,ethnicity, weight, height, occupation, or another demographic attributeof the patient. Physical attributes can include retinal image quality,axial length, iris color, topography, corneal curvature, aberration ofhigher order than spherical or cylindrical aberration, or anotherattribute of the eye, or attribute of a patient's body, which may havesome correlation with difference between objective and subjective eyerefraction results.

The determination module can be configured to predict the subjectiverefractive preference using a correlation developed from a databaseincluding respective demographic or physical attributes and respectiveobjective eye properties for many different eye patients. A databasestoring the respective attributes can be included in the memory 470illustrated in FIG. 4, or in an external server accesses via the networkinterface 468 in FIG. 4, for example.

In one example, objective and subjective refraction results along withrespective ages for many patients examined using an embodiment apparatuscan be stored in memory in the apparatus. A determination and controlmodule in the apparatus can determine that the difference betweenobjective and subjective refraction results for the apparatus variesapproximately linearly with age of the patient, for example. Then, basedon this linear correlation, the determination and control module canpredict subjective refraction for a given patient of given age based onthe given patient's objective refraction results and the patient's age.

In another example a determination and control module may determine thatthe difference between objective and subjective refraction results forthe apparatus diminishes with the magnitude of the objective refractionresults themselves roughly according to a quadratic function. Thus, fora given patient, based on the patient's objective refraction results andthe quadratic function, the determination and control module may predictthe given patient's subjective refractive preference. The visual tunablelens can then be set to the predicted subjective preference, and furthersubjective examination may optionally be performed.

It should also be noted that such predictive methods can also be appliedto data obtained from devices that only perform objective refraction.Objective results from a wavefront aberrometer, for example, may becompared with subjective phoroptry results over a large sample ofpatients to develop predictive correlations that can be applied toobtain (effectively) subjective-quality refractive corrections on thebasis of objective measurements alone. Nevertheless, it is preferable todevelop the correlation between objective and subjective refraction, andthe prediction of subjective refractive preference, on the basis ofobjective and subjective measurements acquired using the same apparatuswithin the same examination session. Use of the same apparatus in thiscontext can potentially be faster and more consistent.

The determination module 120 in FIG. 1 or the determination and controlmodule 220 in FIG. 2, or another processor that is part of, or separatefrom, the apparatus in FIGS. 1-2, for example, can perform calculationsto predict a subjective refractive preference of a person having the eyebased on the property of the eye based on the wavefront. This can bedone by comparing, over time, the difference between refractivepreferences (phoroptic-type determinations) and objective refractionvalues as a function of various patient attributes, such as thedemographic and physical attributes described hereinabove. Variousmethods and calculation routines can depend upon the empirical datacollected over time. Methods may be used that take into account age,gender, the absolute objective refraction value for the eye, or anyother value for the user that may have a correlation with the differencebetween objective and subjective refractive values. In this way,prediction of subjective refraction, even based on objective refractionalone, may be improved over time.

Column 821 d illustrates an example procedure for obtainingaccommodation amplitude (range) measurements based on patient feedback.At 845, the apparatus 200 goes into accommodation measurement mode(presbyopia measurement mode). At 847, push-up or minus-lens techniqueis used or “add” mode is used to determine a prescription for readingglasses to deal with presbyopia. At 849, a final accommodation amplitudeis obtained.

In order to measure accommodation amplitude (either with push-up orminus-lens technique), it can be assumed that the person who is beingtested is emmetropic (i.e. requires no corrective lenses for distancevision) or is properly corrected for distance vision (for example, witheyeglasses or contact lenses). Embodiment devices such as the QuickSeeapparatus can provide proper correction for distance vision via a visualtunable lens, which can take the place of a phoropter or set of triallenses.

The visual tunable lens can be especially advantageous when using theminus lens method to measure accommodation. Traditionally, for the minuslens method, the accommodative demand of a small nearpoint target ischanged as minus lenses are introduced to the patient monocularly untilthe target is no longer clear, based on patient feedback. However, witha visual tunable lens-based apparatus according to embodiments, noadditional lenses need to be carried around, and the introduction ofmore minus power can be done continuously, instead of in a step-wisefashion as done traditionally. The capability for continuously variablepower is expected to result in a more accurate measurement ofaccommodation amplitude.

The procedure illustrated in column 821 d using embodiment methods andapparatuses differs significantly from existing methods foraccommodation measurement. Existing methods typically include using aphysical moving target attached to a phoropter. The physical movingtarget starts a distance away from the person (to correct for distancevision) and is gradually moved towards the patient's eye to track thepatient's myopia. At a sufficiently small distance between the eye andmovable target (closer than the near point), the eye can no longeraccommodate. Existing systems using a moving target can havedisadvantages of being physically large, requiring moving parts,requiring actuators for the movement, lacking the ability to cyclebetween settings quickly, potentially having drift or hysteresis, andcausing the eye to over- or under-accommodate if the physical target ismoving during measurement and the movement is perceived by the eye oreyes under test. In contrast to existing systems, embodiments describedherein can take advantage of a tunable lens for fast, repeatable,accurate accommodation measurements without mechanical moving parts.

A further advantage of embodiments described herein, in contrast toexisting methods and systems, is that objective accommodationmeasurements can be obtained by acquiring wavefront measurements at anytime during or between changes to the tunable lens settings, all whilethe patient views the same distant target through the tunable lens whosesettings are changed as needed. In this manner, a very precisedetermination of accommodation can be obtained, which is not possiblewith existing methods and systems, even where both lens systems andwavefront aberrometers are both used in the same setting but as part ofdifferent systems.

In some embodiments, no subjective feedback from the patient is evenrequired for an accommodation measurement, because wavefrontmeasurements are iteratively made while the tunable lens setting ischanged until the wavefront measurements indicate that accommodation isno longer occurring. The accommodation amplitude measurement can becompleted more rapidly since there is no need to wait for the patient'sverbal responses. Patients that are asked to provide subjective feedbackduring an eye examination, such as an accommodation range examination,are often stressed about their feedback and even question their ownfinal results because they are not sure whether their responses havebeen “correct.” The objectivity that can be provided by an embodimenttunable lens and wavefront aberrometry combined system can eliminate thestress of these patients. The results can be more repeatable becausethey are not affected by a patient's anxiety regarding “correct”responses and because of the inherent precision of wavefrontaberrometry. The accuracy of the measurements using embodimentsdescribed herein can also be more reliable because patient communicationissues (e.g., with children, elderly patents, patients that do not speakthe same language as a clinician, etc.). An example embodiment methodfor determining accommodation using an embodiment combined tunable lensand wavefront aberrometry apparatus is further described hereinafter inconnection with FIG. 9E.

FIGS. 9A-9F supplement the overall refractive examination flow diagramin FIGS. 8A-8B by illustrating in further detail how specific portionsof the flow diagram in FIGS. 8A-8B can be carried out.

FIG. 9A shows a procedure 900 a in flow diagram form illustrating ingreater detail how a lensometry measurement may be performed usingembodiment apparatuses and methods, as illustrated in summary at element818 in FIG. 8B. At 951 a, a lensometry attachment, such as theattachment 591 in FIG. 5A, is attached to an embodiment device.Eyeglasses such as eyeglasses 598 in FIG. 5A are placed into theattachment. At 951 b, light is sent into the eyeglass lens along anoptical path. For example, eye illumination light 240 (illustrated inFIG. 2) can travel along the path illustrated in FIG. 2, exit theapparatus through the tunable lens 110, and enter into the lensometryattachment 591.

At 951 c, the wavefront of light from the eye, particularly from theartificial eyes 599 illustrated in FIG. 5A, is measured. The light isreceived via an optical path from the lens on the attachment, similar tothe light 108 illustrated in FIG. 2. At 951 d, the refractive profile ofthe eyeglass lens is determined by a module, such as the determinationand control module 220 illustrated in FIG. 2. At 951 e, a refractiveprofile of the eyeglass lens is stored in the determination and controlmodule 220.

FIG. 9B is a flow diagram illustrating in greater detail how speckle inwavefront measurements can be suppressed using embodiment apparatus andmethods, particularly by taking advantage of tunable lenses. In aprocedure 900 b illustrated in in FIG. 9B, at 953 a, light is sent froman illumination light source (e.g., source 238 in FIG. 2) along anoptical path through a light source tunable lens (e.g., lens 210 in FIG.2) and through the visual tunable lens (e.g., lens 110 in FIG. 2). At953 b, a wavefront of the light is shaped by changing the focal power ofthe light source tunable lens, or the visual tunable lens, or both. Thiswavefront shaping can be similar to the iterative shaping illustrated inFIG. 6, for example. At 953 c, small variations in the wavefront of thelight are introduced, by oscillating the focal power of the light sourcetunable lens, the visual tunable lens, or both, to randomize the specklepattern generated at the eye and the wavefront sensor.

FIG. 9C is a flow diagram illustrating in greater detail how objectiverefractive measurements may be obtained using the embodiment apparatusand methods, particularly by taking advantage of a visual tunable lensaccording to an objective refraction procedure 900 c. At 955 a, light issent from an illumination light source, to an eye, along an optical paththrough a light source tunable lens and a visual tunable lens. Both thelight source tunable lens and visual tunable lens are initially set toapply zero focal power. At 955 b, light that is reflected orbackscattered from the retina of the eye is passed through the visualtunable lens to a wavefront sensor.

At 955 c, a wavefront of the light from the eye is measured. At 955 d,the refractive error (e.g., spherical and astigmatic) of the eye isestimated based on the measured wavefront, together with focal powerapplied subsequently by the visual tunable lens and light source tunablelens, as described hereinabove in connection with FIG. 6, for example.At 955 e, appropriate focal powers (e.g. spherical and astigmatic) areapplied by the visual tunable lens and light source tunable lens tonegate an estimated refractive error of the eye to the greatest degreepossible in view of the quality and available adjustments of the tunablelenses. At 955 f, elements 955 c, 955 d, and 955 e are repeated until anestimated refractive error of the eye is stable to within an acceptablelevel of variation (e.g., 0.25 dpt, 0.15 dpt, or 0.05 dpt).

FIG. 9D is a flow diagram illustrating in further detail how subjectiverefractive measurements can be obtained using embodiment apparatus andmethods, according to a subjective refraction procedure 900 d. At 957 a,a visual tunable lens is set to negate refractive error of the eye ofthe user, where the refractive error is estimated from an objectiverefraction process such as that illustrated in FIG. 9C. At 957 b,spherical and astigmatic power of the visual tunable lens are variedsystematically (in line with standard subjective refraction practices),either automatically through a predefined method, or by manual inputfrom the eye patient or an assistant.

At 957 c, eye patient feedback is requested regarding comfort and visualacuity after each change of power of the visual tunable lens. At 957 d,elements from 957 b-c are repeated until an eyeglass prescription forthe eye patient has been fully determined in line with standardsubjective refraction procedures (e.g., using a phoropter). Accordingly,because subjective refraction as illustrated in example FIG. 9D may useobjective results from example FIG. 9C as a starting point, refractiveprescriptions and other properties determined by a determination modulesuch as the module 120 illustrated in FIG. 1 or the determination andcontrol module 220 illustrated in FIG. 2 can be based on both thewavefront aberrometry (objective results) and the tunable-lens-basedphoroptry (subjective results) from the same apparatus.

FIG. 9E is a flow diagram illustrating an example accommodationprocedure 900 e that shows how embodiment devices and methods can beused to measure accommodation amplitude for evaluation of presbyopia. At959 a, a visual tunable lens is set to negate refractive error of apatient's eye as determined by subjective refraction. At 959 b, thepatient is requested to view through the apparatus toward a target withsmall text or symbols, such as a reduced Snellen chart, for example,placed at typical reading distance away from the eye, about 0.4 meters.

At 959 c, minus optical power is added to the visual tunable lensgradually until the small text or symbols on the target become, andremain, blurred based on feedback from the patient. At 959 d,accommodation amplitude of the patient's eye is determined by adding thetotal minus power of the visual tunable lens to the reciprocal of thedistance of the target (about 1/0.4 m).

While patient feedback in combination with tunable lens adjustmentsalone may be used to determine accommodation range, a particularadvantage of embodiments described herein, including those with both awavefront sensor and tunable lens in the same apparatus, is thataccommodation may be measured in a more automated fashion by takingadvantage of wavefront measurements in combination with tunable lensadjustments. As an example, objective and subjective refractivemeasurements may be performed first, as outlined in FIGS. 8A-8B or inFIGS. 9C-9D. This can provide final corrective prescription for thepatient, initially without regard to accommodation range, and the visualtunable lens may be set to the final settings. Subsequently, theapparatus may measure an initial corrected wavefront with these tunablelens settings, and the apparatus may then change the tunable lens focalpower very slowly in small steps, allowing for the patient's given eyeunder test to accommodate while still viewing the fixed target indicia.

At each lens adjustment step, after appropriate accommodation, anadditional wavefront measurement can be automatically acquired by theapparatus, saved, and monitored by the determination module. After asufficient number of steps in focal power, when the determination moduleeventually determines that the measured wavefront has deviated at leasta minimum threshold from the initial corrected wavefront value (orotherwise determines from the wavefront measurements that the eye undertest is no longer sufficiently accommodating), then the determinationmodule may determine that a difference between the tunable lens focalpower at the final optimized settings and the focal power at the pointof maximum accommodation is the accommodation range of the patient'seye. As will be understood in view of this description, accommodationmeasurements such as those described above may also be performedaccording to binocular embodiments on both eyes at the same time.

FIG. 9F is a flow diagram illustrating an example machine learningprocedure 900 f showing how machine learning can be implemented inembodiment devices and methods to predict subjective refractivepreferences of an eye patient based on objective measurements. At 961 a,patient data including at least a refractive error estimated byobjective refraction and a refractive error determined by subjectiverefraction are stored in a database. The database can include the memory470 in FIG. 4 or a database external to an embodiment apparatus, such asa network database accessed via the network interface 468 in FIG. 4, forexample.

At 961 b, a mathematical model from the database (e.g., derived frommachine learning techniques) is used to predict refractive errordetermined by subjective refraction given refractive error estimated byobjective refraction, as determined according to FIG. 9C, for example.At 961 c, predicted refractive error is used as an initial startingpoint for subjective refraction, as carried out according to FIG. 9D,for example.

FIGS. 10A-10B are flow diagrams illustrating successive parts of asingle embodiment procedure 1000 for determining subjective refractivepreferences of a patient using embodiment apparatuses. It should beunderstood that the procedure illustrated in FIG. 9D for subjectiverefraction is a general procedure that can further include manydifferent variations using embodiment apparatuses. In general, theprocedure 1000 in FIGS. 10A-10D is a particular variation that includesiterative determination of coarse and fine subjective refractivepreferences for a given eye and allows a patient to interact directlywith an apparatus having interactive features to determine thesubjective preferences. This can be done with smart, iterative controlof visual-tunable-lens vision correction values using interactivepatient feedback.

In some embodiments consistent with this disclosure, an optometrist orassistant asks the patient which correction settings for the visualtunable lens are subjectively better, iteratively, as refractive valuesof the visual tunable lens are changed, similar to the iterativeprocedure used in standard, optometrist-assisted phoroptry measurements.However, in the procedure 1000, the embodiment apparatus requests thatthe patient turn the dial 356, which is set to control certainrefractive values of the visual tunable lens, iteratively, over coarseand then fine ranges, and the device records the final settings made bythe patient to refine subjective preferences. Each time the patient isasked by the device, through the speaker 362 illustrated in FIG. 3, tooptimize a setting, the patient turns the dial 356 on the housing of theapparatus, while viewing a target such as a Snellen chart through theapparatus, until the patient is satisfied that he or she has adjustedthe dial such that the visual tunable lens is set to the best value forvisual acuity. Then, the apparatus automatically records the optimumtunable lens parameter found by the patient, as particularly describedhereinafter. In other embodiments, the communication interface 360 inFIG. 3 may be used only to query the eye patient verbally and receive avoice-recognized verbal response from the patient, such as “one” or“two,” regarding which subjective, refractive preference is better.

Another feature of the example procedure 1000 is that it illustrates howthe orthogonal basis set, spherical equivalent power M, vertical Jacksoncross cylinder J0, and oblique Jackson cross cylinder J45 can be setmutually independently by the apparatus. This is in contrast to otherembodiments that use the standard clinical S, C, & A basis setreferenced hereinabove in relation to FIG. 3, for example. It will beunderstood that an embodiment apparatus that has control over S, C, andA mutually independently may also control M, J0, and J45 mutuallyindependently by a mathematical transformation.

In general, the procedure 1000 includes setting the visual tunable lensto the optimum settings determined from the objective refraction processusing the wavefront aberrometer. An example procedure for determiningobjective refraction is described in connection with FIG. 9C. Thereafterin the procedure 1000, coarse subjective settings are determined. Thisis followed by setting the visual tunable lens to the optimum coarsesubjective refractive value settings and then determining finesubjective refractive settings. The finer subjective refractive settingsare used as the final subjective refractive preference values for thepatient, and a refractive prescription may then be determined based onthe fine subjective settings, for example. It should be understood that“setting the visual tunable lens,” as used herein, can include settingone or more of a plurality of individual tunable lenses opticallyarranged in series, as described hereinabove in relation to FIG. 1.

In greater detail, in FIG. 10A at 1063, the visual tunable lens is setto optimum objective values for M, J0, and J45 (Mopt, J0opt, and J45opt,respectively) previously determined from objective refraction processbased on wavefront aberrometry (see, e.g., FIG. 9C). These optimumobjective values can be stored in the memory 470 illustrated in FIG. 4,and the lens settings can be made in response to commands from theprocessor 472 in FIG. 4, for example. Accordingly, at 1063 a-c, M is setto Mopt, J0 is set to J0opt, and J45 is set to J45opt, respectively.

At 1065, coarse subjective settings Mopt′, J0opt′, and J45opt′ aredetermined. In the procedure 1000, coarse subjective settings aredetermined in the following manner. At 1065 a, the dial 356 is set tocontrol the visual tunable lens such that, over a full range of motionof the dial available to the patient, M will vary over a range ofMopt+/−0.5 dpt while J0 and J45 are maintained constant at J0opt andJ45opt, respectively. At 1065 b, the apparatus, via the speaker 362,instructs the patient to turn the dial 356 iteratively to optimizesubjective visual acuity preference. During this adjustment, a fullrange of motion of the dial 356 only allows adjustment over theMopt+/−0.5 dpt range, such that the patient cannot deviate too far fromthe optimum objectively determined setting. It should be understood thatthe range of +/−0.5 dpt for the coarse adjustment is an illustrativevalue, and this value may be changed and set in the apparatus based onfurther engineering, doctor or optometrist knowledge, machine learningas illustrated in FIG. 9F, demographic factors, or other factors, asnecessary. At 1065 c, the apparatus then saves this value as the coarsesubjective preference Mopt′ and sets the visual tunable lens to thisvalue.

At 1065 d, the apparatus configures itself to control vertical Jacksoncross cylinder J0 in response to a patient adjusting the dial 356. Inparticular, the apparatus sets itself to adjust J0 over a range ofJ0opt+/−0.5 dpt as the dial 356 is adjusted over its full range.Meanwhile, the apparatus maintains the visual tunable lens at constantMopt′ and J45opt. At 1065 e, the patient is requested, through thespeaker 362, to turn the dial 356 iteratively to optimize J0 to anoptimum coarse subjective preference value J0opt′. At 1065 f, theapparatus then saves J0opt′ and sets the visual tunable lens to thisvalue.

At 1065 g, a similar procedure is carried out for the parameter J45. Theapparatus sets itself to control J45 over a range of J45opt+/−0.5 dpt asthe patient turns the dial 356 over its full range, while maintainingconstant values Mopt′ and J0opt′. At 1065 h, the apparatus asks thepatient to turn the dial 356 iteratively to optimize visual acuity, andthe patient finally settles on a preferred setting. At 1065 i, theapparatus saves the setting as the optimum coarse subjective preferencevalue of J45, namely J45opt′. With the coarse subjective refractivesettings having been determined according to the patient's preferences,at 1067, the apparatus proceeds to determine the fine subjectivesettings, as illustrated in FIG. 10B, where the procedure 1000 iscontinued.

In FIG. 10B, in greater detail, at 1069, the apparatus sets the visualtunable lens to the coarse subjective settings determined at 1065 inFIG. 10A, if this has not already been done. Particularly at 1069 a-c,the visual tunable lens set to Mopt′, J0opt′, and J45opt′, respectively.At 1071, fine subjective settings are then determined in a mannersimilar to the manner used to determine the coarse subjective settings,except that the coarse subjective settings are used as the startingpoint instead of the objective settings. An illustrative, example finerange variation of +/−0.2 dpt variation is used for each parameter.However, as noted above in relation to the coarse variation range, thisfine variation range may be selected or set based on additionalinformation or preferences.

At 1071 a, the apparatus is set to respond to the patient's turning ofdial 356 over its full range by controlling M correspondingly over arange of Mopt′±0.2 dpt while maintaining constant J0opt′ and J45opt′. At1071 b, the patient is requested through the speaker to turn the dialiteratively to optimize visual acuity for the particular eye, OD or OS,that is under test. At 1071 c, the fine subjective preference Mopt″ issaved in memory, and the visual tunable lens is set to this value.

At 1071 d, the apparatus sets itself to control J0 over a range ofJ0opt′+/−0.2 dpt in response to the dial being changed over its fullrange, while still maintaining constant Mopt″ and J45opt′. At 1071 e,the apparatus asks the patient to turn the dial iteratively to optimizevisual acuity. At 1071 f, the apparatus records the value J0opt″ andsets the visual tunable lens to this value. At 1071 g, the apparatusconfigures itself to control J45 over a range of J45opt′+/−0.2 dpt inresponse to the dial being turned over its full range. At 1071 h, thepatient is requested to turn the dial iteratively to optimize visualacuity. At 1071 i, the apparatus records the optimum fine subjectivepreference value J45opt″ and sets the visual tunable lens to this value.

At 1073, Mopt″, J0opt″, and J45opt″ are then used as the best subjectiverefractive settings. These values may be set on the apparatus for afinal confirmation from the patient that the settings are valid andacceptable. While not illustrated in FIGS. 10A-10B, the apparatus mayoptionally perform other functions at this point. For example, theapparatus may show the patient corrected and uncorrected views bychanging the visual tunable lens, while speaking to the patientaccordingly, similar to procedures followed by clinicians duringtraditional phoroptry. Furthermore, the apparatus may optionally givethe patient a further opportunity to indicate that additionaladjustments are preferred, either by pressing the trigger switch 397illustrated in FIG. 3 or by the patient answering “yes” through themicrophone 364 illustrated in FIG. 3, for example.

The procedure 1000 may also be repeated for each eye OD and OS in turn.Still further, the procedure 1000 may be modified such that coarsesubjective testing is performed on each eye OD and OS in turn, followedby fine subjective testing on each eye in turn. Furthermore, it will berecognized by those skilled in the art of optometry that there areadvantages in determining subjective refractive corrections of both eyesat the same time. As is known in the art, a patient's preferredcorrection for a given eye may differ depending on whether the other eyeis looking through a correction lens, is uncorrected, or is blocked atthe same time the given eye is evaluated. Accordingly, it will berecognized that, in the binocular arrangements described herein thatallow for simultaneous simulated tunable lens correction for both eyes,the procedure 1000 may be modified such that subjective settings aretested for both eyes synchronously. For example, objectivewavefront-based optimized tunable lens correction settings may be madefor both eyes, followed by the patient or a clinician being directed tochange a dial setting that simultaneously adjusts power or anotherparameter for both eyes together. In this way, a fine or coarsesubjective setting may be determined.

Moreover, the procedure may be modified to include appropriate clinicianinvolvement in any case where it is undesirable or impossible for apatient alone to make adjustments to optimize settings. The valuesMopt″, J0opt″, and J45opt″ may be reported at an interface similar tothe reporting interface screen 354 illustrated in FIG. 3 and used toprovide a refractive prescription. Furthermore, information determinedfrom the procedure 1000, such as final, fine subjective refractivepreferences, may be provided to a patient, clinician, manufacturer viaany of the means described hereinabove or other known means.

It should be understood that the procedure 1000, in other embodiments,can be extended to successively finer adjustments and determinations ofsubjective refractive preference. Furthermore, higher-order refractivecorrections may be determined in a manner similar to that illustrated inthe procedure 1000, where a particular visual tunable lens used in theapparatus permits such adjustments. Those with skill in various types ofmulti-dimensional, iterative optimization, as well as those skilled inthe art of optometry, will understand that “coarse” and “fine”subjective settings can further be determined even where the range ofoptimization (e.g., 0.5 dpt or 0.2 dpt) is the same for both coarse andfine determinations. This is because there is typically value inchanging all the parameters to optimize values, followed byre-optimization of the same values, whether with the same or a smalleradjustment range available to the patient.

Moreover, wavefront aberrometry measurements may be interspersed withsubjective measurements in any location within the procedure 1000 for avariety of purposes. As described hereinabove, embodiments can performadjustments of the variable focal power of the visual tunable lens orlenses iteratively in response to successive wavefront measurements tominimize wavefront errors of the light received from the eye or eyes.Wavefront measurements can be performed in a closed-loop fashion, orsimply performed two or more times in between subjective measurementstaking advantage of the tunable lens. One example includes obtaining aninitial wavefront error measurement, setting a tunable lens to correctfor the initial wavefront error, and then obtaining one or moresecondary or subsequent wavefront measurements.

Performing wavefront measurements on eyes corrected by tunable lensescan allow higher-order corrections to be determined by wavefrontaberrometry with greater accuracy that can be done with the samewavefront aberrometry instrument acting alone. As is known, it is usefulto know higher-order corrections to apply to an eye for improved visionespecially for low-light conditions and other specific cases. As such,embodiments can enable wavefront measurement accuracy commensurate witha very expensive and precise wavefront aberrometer using a relativelymuch more inexpensive wavefront aberrometer. Use of a tunable lens incombination with a wavefront aberrometer in embodiments can enable moreaccurate measurement of higher-order aberrations, even with a relativelylow-cost embodiment system, because the tunable lens can correct theprimary low-order aberrations, thereby cancelling out the contributionsof the low-order aberration (typically much larger), thus enablingbetter detection of the higher-order aberrations with better sensitivityand specificity.

Moreover, embodiments combining tunable lenses with wavefrontaberrometry can enable the subjective test (phoroptry) immediately afterthe objective wavefront aberrometry measurement in situ with the samehandheld apparatus applied to the patient. This can provide betterpatient throughput and accuracy. Further, using embodiments, objectivemeasurements can be performed during the subjective phoroptrymeasurements. In this case, the objective measurements may be used in asituation in subjective phoroptry wherein the patient indicates that itis not clear which tunable lens setting of two or more choices given isbetter, for example.

Marks, Randall et al., “Adjustable adaptive compact fluidic phoropterwith no mechanical translation of lenses,” Optics Letters Vol. 35, No.5, 739-741, Mar. 1, 2010, is hereby incorporated herein by reference inits entirety.

The international Patent Cooperation Treaty (PCT) Applications publishedas WO 2015/003062 A1 and WO 2015/003086 A1 are hereby incorporatedherein by reference in their entireties.

Further, the teachings of all other patents, published applications andreferences cited herein are incorporated by reference in their entirety.

It should be understood that aspects of embodiments of the inventionthat are implemented in software may be stored on various types ofnon-transitory computer-readable media known in the art. The softwaremay be any software that can be loaded and executed by a processor andcause various systems or devices, as applicable, to perform operationsas disclosed herein or as equivalent thereto.

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. An apparatus for determining a property of aneye, the apparatus comprising: a housing including a proximal port, theproximal port configured to receive an eye and to receive light from theeye, the housing further including a distal port, the proximal anddistal ports together forming a visual channel from the proximal portthrough the distal port, the visual channel providing an open view toenable the eye to see target indicia external to and spaced away fromthe housing; a wavefront sensor within the housing, the wavefront sensorbeing configured to receive the light from the eye via the optical pathand to measure a wavefront of the light; and a determination moduleconfigured to determine an objective refractive correction based on thewavefront, the determination module further configured to predict asubjective refractive preference of a person having the eye based on theobjective refractive correction.
 2. The apparatus of claim 1, whereinthe determination module is further configured to predict the subjectiverefractive preference based on a demographic or physical attribute of aperson having the eye.
 3. The apparatus of claim 2, wherein thedemographic or physical attribute includes at least one of an age,gender, ethnicity, weight, height, occupation, or another demographictrait of the person having the eye.
 4. The apparatus of claim 2, whereinthe demographic or physical attribute includes at least one of a retinalimage quality, axial length, iris color, topography, corneal curvature,spherical or cylindrical aberration or axis of the eye, aberration ofhigher order than spherical or cylindrical aberration of the eye,physical attribute of the eye determined from a lensometer measurement,or refractive error of the eye determined by a subjective refraction. 5.The apparatus of claim 1, wherein the determination module is furtherconfigured to predict the subjective refractive preference based on astatistical correlation between subjective refractive preferences andobjective refractive corrections.
 6. The apparatus of claim 1, whereinthe determination module is further configured to predict the subjectiverefractive preference using a correlation developed from a database thatis in apparatus memory or accessed via a network interface, thecorrelation including respective demographic or physical attributes andrespective objective eye properties of a plurality of eye patients. 7.The apparatus of claim 1, wherein the determination module is furtherconfigured to predict the subjective refractive preference using machinelearning.
 8. The apparatus of claim 1, wherein the wavefront of thelight has a minimized wavefront error.
 9. The apparatus of claim 1,wherein the subjective refractive preference differs from the objectiverefractive correction.
 10. The apparatus of claim 1, wherein thewavefront sensor is further configured to obtain a plurality ofwavefront measurements of the light, and wherein the determinationmodule is further configured to determine the objective refractivecorrection based on the plurality of wavefront measurements.
 11. Theapparatus of claim 1, further including one or more visual tunableoptical elements disposed within the optical path and a control moduleconfigured to control a variable focal power of the one or more visualtunable optical elements.
 12. The apparatus of claim 11, wherein the oneor more visual tunable optical elements are configured to oscillate infocal power.
 13. The apparatus of claim 11, wherein the one or morevisual tunable optical elements are configured to minimize or otherwiseoptimize a wavefront error of the light from the eye, and wherein thedetermination module is further configured to determine the objectiverefractive correction for the eye based on the wavefront with minimizedwavefront error.
 14. The apparatus of claim 13, wherein the one or morevisual tunable optical elements are configured to minimize or otherwiseoptimize the wavefront error by optimizing a retinal image qualitymetric.
 15. The apparatus of claim 11, further comprising a manualcontrol configured to be adjustable by a person having the eye to adjustthe variable focal power of the visual tunable lens in accordance withthe subjective refractive preference of a person having the eye.
 16. Theapparatus of claim 11, further comprising a manual control configured tobe adjustable by an operator to adjust the variable focal power of thevisual tunable lens in accordance with the subjective refractivepreference of a person having the eye.
 17. The apparatus of claim 1,further including a lens configured to fog the eye.
 18. The apparatus ofclaim 1, wherein the housing is configured to be gripped by at least onehand of a person to support a full weight of the apparatus during use.19. The apparatus of claim 1, wherein the wavefront sensor is furtherconfigured to obtain a plurality of wavefront measurements of the light,and wherein a determination module is further configured to determinethe objective refractive correction based on the plurality of wavefrontmeasurements.
 20. A method for determining a property of an eye, themethod comprising: passing to an eye, via an open view visual channelfrom a distal port of a housing to a proximal port of the housing, lightfrom target indicia external to and spaced away from the housing;passing the light received from the eye along an optical path;measuring, with the visual channel providing the open view, a wavefrontof the light from the eye, the light received via the optical path fromthe proximal port; determining an objective refractive correction basedon the wavefront; and predicting a subjective refractive preference of aperson having the eye based on the objective refractive correction. 21.The method of claim 20, wherein predicting the subjective refractivepreference is based on a demographic or physical attribute of a personhaving the eye.
 22. The method of claim 21, wherein the demographic orphysical attribute includes at least one of an age, gender, ethnicity,weight, height, occupation, or another demographic trait of the personhaving the eye.
 23. The method of claim 21, wherein the demographic orphysical attribute includes at least one of a retinal image quality,axial length, iris color, topography, corneal curvature, spherical orcylindrical aberration or axis of the eye, aberration of higher orderthan spherical or cylindrical aberration of the eye, physical attributeof the eye determined from a lensometer measurement, or refractive errorof the eye determined by subjective refraction.
 24. The method of claim20, wherein predicting the subjective refractive preference includesusing a statistical correlation between subjective refractivepreferences and objective refractive corrections.
 25. The method ofclaim 20, wherein predicting the subjective refractive preferenceincludes using a correlation developed from a database that is inapparatus memory or accessed via a network interface, the correlationincluding respective demographic or physical attributes and respectiveobjective eye properties of a plurality of eye patients.
 26. The methodof claim 20, wherein predicting the subjective refractive preferenceincludes using machine learning.
 27. The method of claim 20, furtherincluding minimizing a wavefront error of the light from the eye, andwherein determining the objective refractive correction for the eye isbased on the wavefront with minimized wavefront error.
 28. The method ofclaim 20, wherein the subjective refractive preference differs from theobjective refractive correction.
 29. The method of claim 20, furtherincluding obtaining a plurality of wavefront measurements of the light,and wherein determining the objective refractive correction is based onthe plurality of wavefront measurements.
 30. The method of claim 20,further including controlling a variable focal power of one or morevisual tunable optical elements disposed within the optical path. 31.The method of claim 30, wherein controlling focal power includesoscillating focal power.
 32. The method of claim 30, wherein controllingfocal power includes controlling to minimize the wavefront error of thelight from the eye, and wherein determining the objective refractivecorrection is done with minimized wavefront error.
 33. The method ofclaim 32, wherein controlling to minimize the wavefront error includesoptimizing a retinal image quality metric.
 34. The method of claim 30,further including a person having the eye manually adjusting thevariable vocal power of the visual tunable lens in accordance with thesubjective refractive preference.
 35. The method of claim 30, furtherincluding an operator manually adjusting the variable vocal power of thevisual tunable lens in accordance with the subjective refractivepreference.
 36. The method of claim 20, further including fogging theeye.
 37. The method of claim 20, further including a hand of a persongripping the housing to support a full weight of the apparatus duringuse.
 38. The method of claim 20, further including obtaining a pluralityof wavefront measurements of the light and determining the objectiverefractive correction based on the plurality of wavefront measurements.